Magnetization and transport properties of single crystalline RPd${_2}$P${_2}$ (R=Y, La-Nd, Sm-Ho, Yb)

4.9 MB·

by  Gil Drachuck

Magnetization and transport properties of single crystalline RPd P (R=Y, La–Nd,
2 2
Sm–Ho, Yb)
Gil Drachuck, Anna E. B¨ohmer, Sergey L. Bud’ko, and Paul C. Canfield
Department of Physics and Astronomy, Iowa State University, Ames, IA 50011,
USA and Ames Laboratory, Iowa State University, Ames, IA 50011, USA
(Dated: January 13, 2016)
SinglecrystalsofRPd P (R=Y,La–Nd,Sm–Ho,Yb)weregrownoutofahightemperaturesolu-
2 2
tionrichinPdandPandcharacterizedbyroom-temperaturepowderX-raydiffraction,anisotropic
temperature- and field-dependent magnetization and temperature-dependent in-plane resistivity
measurements. In this series, YPd P and LaPd P and YbPd P (with Yb+2) are non local-
2 2 2 2 2 2
moment bearing, whereas CePd P and PrPd P order at low temperature with a ferromagnetic
2 2 2 2
component along the crystallographic c-axis. The rest of the series manifest low temperature anti-
ferromagnetic ordering. EuPd P has Eu+2 ions and both EuPd P and GdPd P have isotropic
2 2 2 2 2 2
paramagnetic susceptibilities consistent with L=0 and J =S = 7 and exhibit multiple magnetic
2
transitions. For R=Eu-Dy, there are multiple, T > 1.8 K transitions in zero applied magnetic
field and for R=Nd, Eu, Gd, Tb, and Dy there are clear metamagnetic transitions at T=2.0 K
6
for H < 55 kOe. Strong anisotropies arising mostly from crystal electric field (CEF) effects were
1
observed for most magnetic rare earths with L (cid:54)= 0. The experimentally estimated CEF param-
0 eters B2 were calculated from the anisotropic paramagnetic θ and θ values and compared to
2 0 ab c
theoretical trends across the rare earth series. The ordering temperatures as well as the polycrys-

n talline averaged paramagnetic Curie–Weiss temperature, θ , were extracted from magnetization
ave
a and resistivity measurements, and compared to the de-Gennes factor.
J

2
1 I. INTRODUCTION surementsweredoneonpolycrystallinesamples,thusthe
anisotropicpropertieswereaveraged-outoverallcrystal-

] lographic directions.
l The RT X (R = Y, La-Lu; T = transition metal;
e 2 2 In the present work, a systematic study of the
- X = Si, Ge, P, As) family of intermetallic com-
r anisotropic magnetic properties and electrical resistiv-
pounds had been extensively studied over the past 50
t
s years [1]. Nearly all RT X compounds crystallize into ity of RPd2P2 single crystals is presented for R = Y,
. 2 2 La-Nd, Sm-Ho, Yb. The experimental techniques used
t the ThCr Si (space group I4/mmm), where the rare
a 2 2 in the crystal growth and characterization are described
m earth(R)ionoccupiesthe2(a)sitewhichhasatetragonal
in Section II. The experimental results are summarized
point symmetry [2]. Moreover, the transition metal ions
- and presented in Section III, starting with x-ray diffrac-
d in this structure, except for Mn [1] (and perhaps Fe in
tion followed by physical properties of R = Y and La
n LuFe Ge [3–5]),bearnomagneticmoments,meaningall
2 2 members, combined, and then separately for all other
o the magnetic properties are a consequence of the R local
c members. Discussions of trends along the series, such
moment. Therareearthionsinteractviathelongrange,
[ as ordering temperature, anisotropic Curie-Weiss (CW)
indirect, Ruderman-Kittel-Kasuya-Yosida (RKKY) type
temperatures and crystal electric field (CEF) effects will
1 interactions, mediated by the conduction electrons [1].
v Therefore,aninterplaybetweenFermisurfacenesting,or bepresentedinSectionIV,followedbyabriefconclusion
5 in Section V.
maximainthegeneralizedmagneticsusceptibility(χ)[6],
2
and local moment anisotropy is expected to lead to a
0
multitude of potential magnetic transitions and ground
3
0 states. Namely, incommensurate or commensurate mag- II. EXPERIMENTAL
. netic propagation vectors, multiple transitions from one
1
0 to the other and metamagnetism are expected. Growth of intermetallic compounds containing signifi-
6 In the specific case of the RPd P , limited work has cantamountsofvolatileelementsisoftenchallengingdue
2 2
1 been done, mainly due to the high cost of palladium and to the apparent conflict between accessible liquidus sur-
v: the difficulties associated with the volatility of phospho- facesandallowablevaporpressure. Overthepastseveral
Xi rusathightemperatures. TheRPd2P2serieswassynthe- years we have been developing mixed metal-chalcogen
sizedinthe1983[7],andexceptoneearlyphoto-emission and metal-pnictogen fluxes that alleviate this problem
r study on EuPd P [8], which revealed that Eu is in a by greatly reducing the partial vapor pressure over the
a 2 2
divalent state, the system has been mainly overlooked. melt. Solutiongrowthusingsulfur[13],nitrogen[14]and
Recently, work has been done on the CePd P com- phosphorous [15] have been possible by careful identifi-
2 2
pound, revealing its ferromagnetic (FM) Kondo-lattice cation and testing of binary melts for use.
nature[9–12]. ThemagneticpropertiesofGdPd P have Given that RPd P crystals have equal amounts of
2 2 2 2
been reported as well [12], but only to serve as reference palladium and phosphorous, the Pd P binary eutec-
67 33
to CePd P . Moreover, all the above mentioned mea- tic (with T (cid:39) 780 ◦C) was identified as a promising
2 2 eu
2

( a ) E u P d P
E u P d P 2 2
4 0 0 0 2 2 )
2
1
(1
)
s
t
3 0 0 0
n
u
o
C
(

y2 0 0 0
it ) )
Intenis1 0 0 0 (002) (101) (110)(103 (004 (200) (202)(114)(211)(105) (213) (204) (220)(116)(222)(215)(301)(312)(224) (008) ( b )
0
2 0 3 0 4 0 5 0 6 0 7 0 8 0
q (
2 d e g )
FIG. 1: (a) Powder X-ray diffraction pattern of EuPd P with (hkl) values for all peak positions. The arrow indicates a peak
2 2
from the Pd-P binary phases (b) Single crystal of EuPd P displayed on a 1 mm grid.
2 2
melt. We first tested the Pd P binary by placing sto- the residual resistivity ratio (ρ(300K)/ρ(2.0K)) mono-
67 33
ichiometric amounts of elemental P and Pd (powder) in tonicallydecreasesacrosstheR+3 membersoftheseries,
one side of a 2ml fritted crucible set [16]. The crucibles again suggesting that as heavier rare earth are used the
weresealedinamorphoussilicatube[17]under0.2atmo- single crystal growth becomes less stable.
spherespartialpressureofArgonandthenheatedover24
DC magnetization measurements were performed in a
hoursto1100◦Cfollowedbydecantingtheliquid. Given
Quantum Design Magnetic Property Measurement Sys-
that there was (i) no apparent phosphorus migration or
tem(MPMS),superconductingquantuminterferencede-
significant vapor pressure at high temperature and (ii)
vice (SQUID) magnetometer (T = 1.8 - 300 K, H =
max
noapparentcrucibleorampuleattack,thePd P melt
67 33 55kOe). Allsamplesweremanuallyalignedwithin5de-
was used for these growths.
greesofaccuracy,tomeasurethemagnetizationalongthe
desiredaxes. Thesamplesweretightlysqueezedbetween
Single crystals of the RPd P (R=Y, La–Nd, Sm–Ho,
2 2 twoplasticstrawsforH (cid:107)ab orientation. Inthisconfigu-
Yb)seriesweregrownoutofselfflux, byadding5−10%
rationthereisnoriskofsamplerotationduetotorquefor
rare earth into the Pd P eutectic [17, 18]. The ini-
67 33 samples with magnetic anisotropy, and no addendum to
tial elements where placed into the bottom 2 ml alu-
the magnetic signal. For the H (cid:107)c orientation, the sam-
mina crucible of a fritted crucible set [16], and sealed
ples where mounted between two strips of Teflon tape
in amorphous silica ampules under a partial argon at-
suspended over the edges of two internal straws inserted
mosphere. The ampules were heated to 300 ◦C in 3
into an external straw. Given that the signal of the mo-
hoursanddwelledtherefor6hours,inordertoallowthe
ment bearing samples was much larger than that from
phosphorous and palladium to react, therefore reducing
the addendum for this configuration, only the data from
the risk for explosions. Subsequently, the ampules were
LaPd P ,YPd P andYbPd P measurementwerecor-
heated over 10-12 hours to 1180 ◦C where they dwelled 2 2 2 2 2 2
rected for addendum contribution.
for 3 additional hours, then cooled, over 90-120 hours to
930 ◦C. At that point, the excess molten flux was de- The temperature-dependent magnetization (M(T)) of
themoment-bearingmembers,wasmeasuredwithanex-
cantedand, givenPd-content, recycled. Thegrowncrys-
ternal magnetic field of H =1 kOe. Due to the tetrago-
talshadplate-likemorphologywiththec-axisperpendic-
nalsymmetryoftheRPd P ,thepolycrystallineaverage
ular to the plate surface. An optical image of EuPd P 2 2
2 2 method, taking χ = 1χ + 2χ , could be applied to
is given as an example in Fig. 1(b). As R progressed ave 3 c 3 ab
eliminate CEF effects [19]. The transition temperatures
pastHo,theRPd P compoundsbecamehardertogrow
2 2
forallantiferromagneticallyorderedcompoundswerein-
in single crystal form. Attempts to grow ErPd P were
2 2
ferred from d(χ T)/dT [20].
unsuccessful,therefore,TmPd P andLuPd P growths ave
2 2 2 2
were not attempted. The fact that YbPd P could be Additional measurements of DC magnetization for
2 2
grown is very likely associated with the fact that Yb is TbPd P and DyPd P up to 140 kOe were performed
2 2 2 2
divalent and its unit cell volume is between GdPd P using an extraction magnetometer of the ACMS option
2 2
and TbPd P . As will be shown in the next section, of a Quantum Design Physical Property Measurement
2 2
3
and/or dρ/dT. The error bars due to mass uncertainty
1 0 . 0
) ( a ) and different ranges of CW fit are about 2% for effective
(Å 9 . 9 Y L a C e N d G d D y c - a x is mθ o.mTenhteaunndce1rt0a%intfyorinpatrhaemsaagtnuertaitcedCWmotmemenptevraatluueresis,
axis 9 . 8 P r S m T b H o esptimated to be about 2% as well.
- Y b
c E u
9 . 7

)
(Å 4 . 2 III. RESULTS

is
x 4 . 1
a a - a x is A. Powder X-ray Diffraction
-
a

4 . 0
1 7 5 ( b ) The unit cell parameters for the RPd2P2 compounds
L a weredeterminedatroom-temperature,usinggroundsin-
) glecrystals,withaRigakuMiniflexpowderX-raydiffrac-
(Å1 7 0 C e E u tometer(CuKαradiation). TheX-raydiffraction(XRD)
e P r pattern ofEuPd2P2 is shown inFig. 1(a)as an example.
m N d Allmajorpeakscanbeidentifiedandareconsistentwith
lu c e ll v o lu m e the reported ThCr Si (I4/mmm,139) tetragonal struc-
o S m 2 2
V1 6 5 ture. Insomecases,smallpeaksassociatedwiththePd-P
ll G d binaryphaseswerealsodetected. Thelatticeparameters,
e Y b
C T b a-axis and c-axis (Fig. 2(a)), were refined for all series
Y D y
1 6 0 H o members and are summarized in Table I. The unit cell
volume is shown in Fig. 2(b). The values are in excel-
lent agreement with previously published data [7]. The
3 6 4 0 6 0 6 5 7 0
trivalent rare earth members of the RPd P series show
2 2
A t o m ic N u m b e r
a standard lanthanide contraction in volume. It is worth
noting that the effects of divalency (for R=Eu and Yb)
are very anisotropic with an ∼ 0.15˚A increase in the a-
FIG. 2: (a) Powder x-ray diffraction a-axis and c-axis unit lattice parameter and a comparable ∼0.15˚A decrease in
cellparameter. (b)Unitcellvolumecalculatedfromtheabove
thec-latticeparameter. Thisisanunusualeffect,sincein
values.
relatedcompounds,forwhichEuisdivalent,suchbehav-
iorwasnotobserved. InEuRu P [23]forexample, only
2 2
c-lattice parameter is increased, in EuCu Ge [24] only
System (PPMS). For these measurements the samples 2 2
a-lattice parameter is increased and in EuCo Ge [25]
were glued to a Kel-F disk to ensure H (cid:107) c direction 2 2
and EuNi Ge [24] both a- and c-lattice parameter are
of the applied field. The signals from the samples were 2 2
increasedrelativetothetrivalentlanthanidecontraction.
significantly larger than the diamagnetic signal from the
disk [21], so no correction for the disk’s signal was used.
Resistivity measurements were performed within the RPd2P2 a (˚A) c (˚A) Volume (˚A3)
temperature-field environment of the MPMS system us- Y 4.05 9.84 161.4
La 4.12 9.89 174.1
ing a Linear Research Inc. LR-700 4-wire AC resistance
Ce 4.16 9.90 171.1
bridge. The samples were shaped into bars with typical
Pr 4.14 9.88 169.5
dimensions of 1.5 × 0.8 × 0.3 mm3 mm. Epotek-H20E
Nd 4.12 9.88 168.1
silverepoxywasusedtocontactPtwires(0.05mmdiam-
Sm 4.10 9.87 165.8
eter)tothesamples. Typicalcontactresistanceswere1–2
Eu 4.16 9.74 170.8
Ω. Theplate-likemorphologyofthecrystalshasonlyal-
Gd 4.08 9.86 164.2
lowedmeasurementswithcurrentflowingintheab-plane.
Tb 4.06 9.86 162.5
Theresistivetransitiontemperaturevalueswereinferred
Dy 4.02 9.85 161.2
from anomalies in dρ/dT [22]. The transition tempera- Ho 4.03 9.84 159.8
tures from magnetization and resistivity measurements Yb 4.10 9.72 163.0
are summarized below in Table II.
The uncertainty in absolute value of resistivity due to
TABLE I: Lattice parameters and unit cell volume of the
the measurement of the sample’s dimension and sample
RPd P series. The uncertainty is ∼0.2% for lattice param-
irregularity is estimated to be ∼ 20%. The uncertainty 2 2
eter values.
in determination of the transition temperature was de-
termined by half width at half maximum for d(χT)/dT
4
B. YPd P and LaPd P their band structures and Fermi surface topologies. For
2 2 2 2
YPd P an upturn in susceptibility is present because
2 2
YPd2P2 andLaPd2P2 exhibitmagneticandelectronic of trace amounts impurities. (e.g Y1−xGdx Pd2P2 with
properties consistent with the empty 4f-shells of Y and x=0.000025 would give a comparable CW tail). The
La ions. The zero-field resistivity (ρ(T)) in Fig.3(a) magnetic signal from the addendum used for the H (cid:107)c
demonstratescharacteristicmetallicbehaviorwithanal- was subtracted for both R=Y and La.
most linear increase of the resistivity with temperature
forT >75K,withnoobservedanomaliesdownto1.8K.
The residual resistivity ratios, RRR≡ ρ(300K)/ρ(2K)), C. CePd2P2
of YPd P and LaPd P are 2.4 and 7.8 respectively.
2 2 2 2

Similar to CeAgSb [26], CePd P is a rare example
2 2 2
of a low-temperature, Ce-based ferromagnet. Although
4 0
(a )
this compound was previously reported, the work has
3 5 beendoneonpolycrystallinesamples[9–12],thereforethe
)
anisotropic characteristics of CePd P were not studied.
m 3 0 2 2
c InFig.4(a)M(T)/H datameasuredabovethesaturation
hm 2 5 field (H=10 kOe) is shown. A ferromagnetic transition
O is apparent at T < 30 K with large anisotropy between
m ( 2 0 theeasy(H(cid:107)c)andhard-axis(H(cid:107)ab)directionsofapplied
istivity 1 5 LY aP Pd d2P2P2 2 fimealdgn.eTtihcefiinelsdetosfhHow=s1MkO(Te.)/H data,measuredinalower
s 1 0 TheH/M(T)dataareplottedinFig.4(b). Byplotting
e I || (a b )
R 5 H = 0 the data in such manner, high temperature anisotropies
becomepronounced,andCWlawbehaviorismoreeasily
0 identified. For the H (cid:107)ab direction, a non-linear feature
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
is apparent in the 150 < T < 50 K region, whereas the
0
ol) - 1 0 (b ) (c ) data T > 150 K, H/Mab(T) exhibit close to linear be-
havior with a CW temperature θ =−344 K. For H (cid:107)c,
/m - 2 0 L a P d P ab
u 2 2 below 150 K, H/Mc(T) deviates from the expected lin-
-60 em -- 43 00 H = 1 0 k O e H || c YH =P 1d02 Pk O2 e eaaCrWformtemaspewrealtlu.rAebθocv=e 16540KK,wHh/icMhci(sTc)oinssilsinteenatr wwiitthh
(1 - 5 0 H || a b the axial ferromagnetic ordering. From the H/Mave(T)
/H - 6 0 H || c dmaotma,eantCoWf µtemp=era2t.4u4rµeofwθaevree=inf−er1r3edK,aslnigdhatnlyesffmecatlilveer
M - 7 0 H || a b eff B
than expected for a free Ce+3 ion (2.54µ ). The exper-
- 8 0 B
0 1 0 0 2 0 0 3 0 0 1 0 0 2 0 0 3 0 0 imental values are in good agreement with the previous
report on polycrystalline sample [12].
T e m p e r a t u r e ( K )
Figure 4(c) presents the anisotropic magnetization
isotherm data measured at T = 2.0 K. The easy
axis (H(cid:107)c) M(H) curve saturates near H = 2 kOe.
FIG. 3: (a) Zero-field, in-plane resistivity of LaPd P and
2 2
YPd2P2 (b) Anisotropic M(T)/H of LaPd2P2 measured at The saturated moment of CePd2P2 is Msat = 1.64µB,
H =10 kOe. (c) Anisotropic M(T)/H of YPd P measured higher than the reported value for polycrystalline sam-
2 2
at H =10 kOe. ples[12],yetlowerthanthepredictmoment(M(T) =
sat
g J) value of Ce+3 (2.14µ ) for free ions. The hard-
J B
Magnetization measurements performed at H = axis(H(cid:107)ab)M(H)curveontheotherhand, showsakink
10 kOe are shown in Fig. 3(b) and (c). Both com- in the linear slope at H = 18 kOe, possibly indicating
pounds present a net diamagnetic susceptibility, im- weak meta-magnetism, but does not saturate up to the
plying that the sum of Landau and core diamagnetic maximal measurement field of H =55 kOe.
contributions to the magnetic susceptibility, is greater Finally,thezero-field,in-planeresistivityasafunction
than the Pauli paramagnetic contribution. In compar- of temperature is shown in Fig. 4(d). The residual resis-
ison, a recent study has revealed that YCo Ge and tivity ratio of CePd P is RRR=12.4. The 4f electronic
2 2 2 2
LaCo Ge are Pauli paramagnetic [25]. The low γ, ∼ contributionofCePd P wasdeducedbysubtractingthe
2 2 2 2
6 mJ/K2 [9] as opposed to 10 mJ/K2 for YCo Ge and resistivity of LaPd P , which should consist primarily of
2 2 2 2
14.6 mJ/K2 LaCo Ge [25], and the diamagnetism of electron-phonon and electron-impurity scattering. The
2 2
YPd P and LaPd P imply that they have a relatively characteristicsoftheresistivitycurve,areconsistentwith
2 2 2 2
small density of states (DOS) at the Fermi surface. The previously reported Kondo-lattice behavior [9], with a
compounds show different anisotropies, probably due to weak minimum in the 4f (ρ = ρ −ρ ) component
4f Ce La
unit cell contraction, which in turn, causes changes in oftheresistivityaroundT =45K.Theferromagnetic
min
5
1 .0 2 .0
( a ) 5 ( c )
ol) 00 ..68 (/Hemu/mol)1234 H = 1 k O e (mnt /f.u.)B1 .5 -1m K)00 ..57 05 ---001 ...680 )/dT HH |||| ca b
(M/Hemu/m 00 ..24 C e P d 2P 2 M00 T1e0m p He r2 a|0|t uc r e (3K0) 4 0 netic Mome01 ..50 rmW d/dT (c00 ..02 05 0T e 1m 0p e2r0a tu3 r0e 4(K0 ) 00-- 00..20..24 d(M/Have TC =e 2P dK 2P 2
H = 1 0 k O e H || a b g
a
M
0 .0 0 .0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 1 0 2 0 3 0 4 0 5 0
T e m p e r a tu r e ( K ) M a g n e tic F ie ld ( k O e )

6 0 0
( b ) H || c 7 0
( d )
H || a b
5 0 0 A v e ra g e 6 0
u) )
(H/Mmol/em234 000 000 mWistivity ( cm2345 0000 C err Pt4oftd P
s 2 2
1 0 0 C e P d 2P 2 e H = 0
H = 1 k O e R1 0 I || (a b )
0 0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
T e m p e r a tu r e ( K ) T e m p e r a tu r e ( K )
FIG. 4: Measurements of CePd P . (a) Anisotropic M(T)/H measured at H = 10 kOe. Inset: Low temperature blow
2 2
up of anisotropic M(T)/H measured at H = 1 kOe (b) Anisotropic and polycrystalline averaged H/M(T) (c) Anisotropic
magnetizationisothermmeasured atT =2.0K. Inset: low-temperatureblowupof dρ/dTand d(M /H)/dT. (d)Zero-field,
ave
in-plane resistivity (blue) and the 4f electronic contribution (ρ =ρ −ρ ) (dashed magenta)(see text for details).
4f Ce La
ordering is evident with a sharp drop in the resistivity Figure 5(b) depicts the inverse magnetization. The
below the Curie temperature T , nearly to zero 4f resis- paramagnetic anisotropy is less extreme than in
C
tivity at T = 2.0 K, on account of loss of spin-disorder CePd P . Both H/M (T) and H/M (T) show linear
2 2 ab c
scattering, as the ferromagnetic order sets in. T was behavior with a CW temperature θ = −55 K and
C ab
estimated from the temperature dependence of the re- θ = 32 K. The polycrystalline averaged H/M (T) is
c ave
sistivity, by taking the derivative of ρ(T). The jump in linear with a CW temperature of θ = −8 K and an
ave
dρ/dT (insetofFig.4(c))yieldsT =28.4±0.4Kwhich effectivemomentofµ =3.52µ . Thevalueofinferred
C eff B
is consistent with the temperature at which a jump in moment is consistent with the predicted value for a free
d(M(T) /H)/dT occurs. Pr+3 ion (3.58µ ).
ave B
Figure 5(c) presents the anisotropic magnetization
isotherm data measured at T = 2.0 K, confirming the
D. PrPd P FM nature of PrPd P . The M(H) curve for the easy
2 2 2 2
axis (H(cid:107)c) rapidly saturates at H = 5 kOe. The
hard-axis (H(cid:107)ab) M(H) curve on the other hand, lin-
As shown in Fig. 5(a), PrPd P is the other ferromag-
2 2
early increases up to the maximal measurement field of
neticmemberintheRPd P series. M(T)/H data,mea-
2 2
H = 55 kOe. The saturated moment of PrPd P is
sured at H =10 kOe, above the saturation of PrPd P , 2 2
2 2 M =2.10µ , smallerthanthepredictedvalueofPr+3
are strongly anisotropic with M (T)/H (cid:29)M (T)/H in sat B
c ab
(3.2µ ) for free ions.
the ferromagnetic state. The inset shows M(T)/H data B
measured at H = 1 kOe. The easy-axis (H(cid:107)c) shows a Thezero-field,in-planeresistivity(Fig.5(d))isroughly
clear transition just below 10 K after which the magne- linear from 300 K down to around 30 K. The residual
tization saturates. resistivity ratio of PrPd P is RRR=7. The FM order-
2 2
6
2 .5
1 .2 ( a ) ( c ) P rP d 2P 2
H || c .)
1 .0 P rP d 2P 2 H || a b /f.u2 .0
B
(/Hemu/mol)000 ...468 H = 1 0 k O e (M/Hemu/mol)1234 H = 1 k O e (metic Moment 11 ..05 HH |||| ca b rmW -1d/dT (cm K)0000 ....0123 0 5 1 0 1 5 2 0 2 50--01.0..50 )d(M/H/dTave
M0 .2 00 5 1 0 1 5 2 0 2 5 gn0 .5 T e m p e ra tu re (K )
T e m p e ra tu re (K ) a T = 2 K
M
0 .0 0 .0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 1 0 2 0 3 0 4 0 5 0
T e m p e r a tu r e ( K ) M a g n e tic F ie ld ( k O e )
2 5 0
( b ) P rP d P 4 0 ( d )
2 2
2 0 0
H = 1 k O e
)
) m3 0
u1 5 0 c
m W P rP d P
(mol/e1 0 0 mtivity (2 0 2 2 W cm) 667 ...050
H/M5 0 HH |||| ca b esis1 0 H = 0 rm( 55 ..05
A v e ra g e R I || (a b ) 0 T e5m p1e0ra tu1 r5e (2K 0)
0 0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
T e m p e r a tu r e ( K ) T e m p e r a tu r e ( K )
FIG. 5: Measurements of PrPd P . (a) Anisotropic M(T)/H measured at H = 10 kOe. Inset: Low temperature blow up
2 2
of anisotropic M(T)/H measured at H = 1 kOe. (b) Anisotropic and polycrystalline averaged H/M(T). (c) Anisotropic
magnetization isotherm measured at T =2.0 K. Inset: low temperature blow upof dρ/dT and d(M /H)/dT. (d) Zero-field,
ave
in-plane resistivity. Inset: low-temperature blow up of ρ(T).
ing is evident with a sharp drop in the resistivity below rections are identical. For H (cid:107)c, NdPd P shows a
2 2
T ,associatedwithlossofspin-disorderscatteringwhich clear metamagnetic transition at H = 3 kOe. The
C
is clearly seen in the inset. The Curie temperature es- magnetization in H (cid:107)ab monotonically increases, crosses
timated from the jump in dρ/dT (inset of Fig 5(c)) is H (cid:107)c curve at 30 kOe and reverse the anisotropy at
T =8.4±0.3 K, in agreement with the peak tempera- H = 30 kOe. Neither for H (cid:107)ab nor for H (cid:107)c direction,
C
ture in d(M (T)/H)/dT. the M(H) curve reaches the predicted saturated moment
ave
predicted for Nd+3 (3.27µ ) up to 55 kOe.
B
The zero-field, in-plane resistivity is depicted in
E. NdPd P
2 2 Fig. 6(d). The residual resistivity ratio of NdPd P is
2 2
RRR=5.4. ρ(T) decreases linearly down around 25 K.
The M(T)/H data of NdPd P (Fig. 6(a)), measured Below25K,theresistivitystartstosaturate. At15K,a
2 2
at H = 1 kOe, are only weakly anisotropic with χ > change of slope is observed. In dρ/dT a minimum is evi-
c
χ . The M(T)/H curves follow a CW law for both dent,followedbyapeakatT =6.0±1Kasdemonstrated
ab
measurement directions. From the H/M(T) data shown intheinsetofFig5(c). Ataclosetemperature,achange
in Fig. 6(b), θ =−25 K, θ =−2 K and θ =−19 K ofslopeisobservedind(χ T)/dT. FromM(T)/H and
ab c ave ave
CW temperatures were inferred. The effective moment ρ(T) data there appears to be a weak signature which
µ =3.64µ is in good agreement with the theoretical could be associated with magnetic ordering near 6 K.
eff B
value for Nd+3 (3.62µ ). M(H) data are consistent with an AFM ground state.
B
The anisotropic magnetization isotherm data mea- Given that the rest of the RPd P compounds also or-
2 2
sured at T = 2.0 K are shown in Fig. 6(c). Up to der antiferromagnetically (see below), we propose that
H = 3 kOe, the M(H) curves of H (cid:107)c and H (cid:107)ab di- NdPd P also adopts AFM order below T ≈6 K.
2 2 N
7
2 .0
( a ) -1)0 .1 5 0 .0 4 T ( c )
u/mol) 00 ..23 HN =d P1 dk 2OP e2 (M/Hemu/mol)000 ...123 0 5 1 0 1 5 2 0 (ment /f.u.)B11 ..05 rmW d/dT (cm K00 ..01 50 T 0e m 5p e r1a0tu1re5 (2K0) 00 ..00 02 cd(T)/dave
(em T e m p e ra tu re (K ) Mom HH |||| ca b
/H 0 .1 H || c tic0 .5 N d P d P
M H || a b ne 2 2
g T = 2 K
a
0 .0 M0 .0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 1 0 2 0 3 0 4 0 5 0
T e m p e r a tu r e ( K ) M a g n e tic F ie ld ( k O e )
2 0 0
7 0
( b ) ( d )
6 0
1 5 0 N d P d P
N d P d P ) 2 2
(mol/emu)1 0 0 H = 1 k 2O e2 mWity ( cm 345 000 IH |=| (0 a b ) m)1 5
H/M 5 0 HH |||| ca b esistiv 2 0 rmW ( c111 234
A v e ra g e R 1 0 0 1 0 2 0 3 0
T e m p e ra tu re (K )
0 0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
T e m p e r a tu r e ( K ) T e m p e r a tu r e ( K )
FIG. 6: Measurements of NdPd P . (a) Anisotropic M(T)/H measured at H = 1 kOe. Inset: low-temperature blow up
2 2
of M(T)/H. (b) Anisotropic and polycrystalline averaged H/M(T). (c) Anisotropic magnetization isotherm measured at
T = 2.0 K. Inset: low-temperature blow up of dρ/dT and d(χ T)/dT. (d) Zero-field, in-plane resistivity. Inset: low-
ave
temperature blow up of ρ(T).
F. SmPd P (Fig. 6(c)) show a linear increase up to H = 55 kOe
2 2
with a slight anisotropy in favor of H (cid:107)c.
The zero-field, in-plane resistivity is plotted in
The M(T)/H data of SmPd P are rather dif-
2 2
Fig. 7(d). The residual resistivity ratio of SmPd P is
ferent from the previous members. As shown in 2 2
RRR=3.8. ρ(T) decreases linearly down to 25 K. Below
Fig. 7(a), the M(T)/H data are anisotropic, with
50K,theresistivitysaturates,thendecreasesslightlybe-
a change of anisotropy around 30 K (below which
low10K.AtT =3.1±0.3Kapeakindρ/dTisapparent,
M (T)/H > M (T)/H), and another change to
ab c
and coincides with the AFM transition in d(χ T)/dT.
M (T)/H >M (T)/H below7K.AtT =3.50±0.3K, ave
c ab N
an anomaly is observed for both M (T)/H, M (T)/H
ab c
and in d(χ T)/dT data (insets of Fig 7(a,c)), which
ave
likely indicates antiferromagnetic (AFM) ordering. G. EuPd P
2 2
From H/M(T) data (Fig. 7(b)), it is clear that the
paramagnetic susceptibility of SmPd P does not follow Figure 8 presents measurements done on EuPd P .
2 2 2 2
a CW law up to 300K, and appears to saturate roughly The temperature-dependent susceptibility (Fig. 8(a)), is
at room temperature. Similar behavior has been re- isotropic down to ∼ 20 K. Around 19 K, a pronounced
ported for other Sm bearing compounds [25, 27–29]. A peak indicating AFM ordering of the Eu moments is ob-
likelyexplanationforthiscouldbethermalpopulationof served. Given that M (T)/H is essentially temperature
c
the Sm3+’s Hund’s rule excited states. The anisotropic independent for 10 K below the peak, the ordered mo-
magnetization isotherm data measured at T = 2.0 K ments are likely aligned perpendicular to the crystallo-
8
0 .0 0 4 0 .0 4
( a ) 0 .0 6 0 .0 6
u/mol)00 ..00 00 23 SH m= 1P kd O2 P e2 (M/Hemu/mol)0000 ....0000 0000 2334 5050 0 2 4 6 8 1 0 (ment /f.u.)B00 ..00 23 rmW -1d/dT (cm K)000 ...000 024 0 T e2 m p4 e r6a tu8re 1 (0K )000 ...000 024 cd(T)/dTave
(em T e m p e ra tu re (K ) Mom TS =m 2 P Kd 2 P 2
/H0 .0 0 1 tic0 .0 1 ( c )
M e H || c
H || c n
g H || a b
H || a b a
0 .0 0 0 M0 .0 0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 1 0 2 0 3 0 4 0 5 0
T e m p e r a tu r e ( K ) M a g n e tic F ie ld ( k O e )
1 2 0 0 ( b ) 5 0 ( d ) S m P d P
2 2
1 0 0 0
)4 0
u) 8 0 0 cm H = 0
l/em 6 0 0 mW (3 0 I || ( a b ) 1 1 .6
(mo 4 0 0 tivity2 0 cm)11 11 ..24
H/M 2 0 0 SH m= 1P kd O2 P e2 HH |||| ca b esis1 0 rmW (1 1 .0
R 0 5 1 0 1 5 2 0
A v e ra g e
T e m p e ra tu re (K )
0 0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
T e m p e r a tu r e ( K ) T e m p e r a tu r e ( K )
FIG. 7: Measurements of SmPd P . (a) Anisotropic M(T)/H measured at H = 1 kOe. Inset: low-temperature blow up
2 2
of M(T)/H. (b) Anisotropic and polycrystalline averaged H/M(T). (c) Anisotropic magnetization isotherm measured at
T = 2.0 K. Inset: low-temperature blow up of dρ/dT and d(χ T)/dT. (d) Zero-field, in-plane resistivity. Inset: low-
ave
temperature blow up of ρ(T).
graphic c-axis over this temperature range. On the en- is linear down to ∼50 K. Below 25 K, at least four tran-
larged temperature scale shown in the inset of Fig. 8(a), sitions can be clearly seen. By looking closer at dρ/dT
multiple features can be identified clearly. andd(χ T)/dT(insetofFig.8(c)),acascadeoftransi-
ave
From the polycrystalline average H/M(T) shown in tionsisapparentatT1 =18.2±0.3K,T2 =12.4±0.5K,
Fig. 8(b), an effective moment µeff = 7.60µB and an T3 = 9.8±0.3 K and T4 = 5.8±0.3 K. The first tran-
average CW temperature θ = −30 K were evaluated. sition can be associated with an opening of a superzone
ave
The size of the effective moment is consistent with the gap. Such a complex magnetic ground state has been
anomalousunitcellvolumeofEuPd P ,showninTableI previously reported for CeSb [31], where six transition
2 2
and Fig. 2(b), both suggesting that Eu is in a divalent at H =0 were identified. More advanced probes will be
state. This is in agreement with M¨ossbauer [8] and pho- necessary to determine the exact nature and number of
toemission spectroscopy [30]. the observed transitions.
The anisotropic magnetization isotherm data, mea-
sured at T = 2.0 K is shown in Fig. 10(c). The M(H)
curveforH (cid:107)c directionhasalinearfielddependenceup H. GdPd2P2
to 55 kOe, whereas the M(H) curve of H (cid:107) ab reveals a
metamagnetic transition at around H = 35 kOe. Above Figure 9 shows measurements done on GdPd P . The
2 2
thetransition,H (cid:107)abandH (cid:107)cM(H)curvesmerge. At M(T)/H data (Fig. 9(a)), similarly to EuPd P , are
2 2
the maximum applied field of 55 kOe the magnetization isotopic down to 20 K. GdPd P exhibits two mag-
2 2
reaches 1.4µB, far below the theoretical value of 7µB for netic transitions around 10 K, one peak in Mab(T)/H at
a free Eu+2 ion. ∼ 11 K followed by a second peak in M (T)/H around
c
In Fig. 8(d), the zero-field resistivity of EuPd P is 7 K, as can be clearly seen in the inset of Fig. 9(a).
2 2
shown. The residual resistivity ratio is RRR = 10. ρ(T) The inverse susceptibility is depicted in Fig. 9(b).
9
0 .1 5
ol)0 .1 0 ( a ) u/mol)00 ..11 24 HE =u 1P 0d 2kP O 2 e (mnt /f.u.)B11 ..05 mW -1/dT (cm K)024 000 ...011 505 cd(T)/dTave ( c )
u/m (em0 .1 0 H = 1 k O e me rd 0 T e m 1p0e ra tu2r0e (K )3 0 E u P d P
(/Hem0 .0 5 H || c M/H0 .0 8 0 T e m p2e0ra tu re (K4 )0 etic Mo0 .5 T = 2 H 2K ||2 c
M n
H || a b ag0 .0 H || a b
M
0 .0 0
5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 1 0 2 0 3 0 4 0 5 0 6 0
T e m p e r a tu r e ( K ) M a g n e tic F ie ld ( k O e )
5 0 7 0
E u P d P
( b ) 6 0 (( dd )) 2 2
4 0
E u P d 2 P 2 )5 0 H = 0
) m
u H = 1 0 k O e c I || ( a b )
m 3 0 W 4 0
(H/Mmol/e 2 0 HH |||| ca b msistivity (23 00 rmW( cm)112 050
1 0 A ve ra g e Re1 0 5
0 5 1 0 1 5 2 0 2 5 3 0
T e m p e ra tu re (K )
0 0
5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
T e m p e r a tu r e ( K ) T e m p e r a tu r e ( K )
FIG. 8: Measurements of EuPd P . (a) Anisotropic M(T)/H measured at H = 10 kOe. Inset: low-temperature blow up
2 2
of M(T)/H measured at H = 1 kOe. (b) Anisotropic and polycrystalline averaged H/M(T). (c) Anisotropic magnetization
isothermmeasuredatT =2.0K.Inset: low-temperatureblowupofdρ/dTandd(χ T)/dT. (d)Zero-field,in-planeresistivity.
ave
Inset: low-temperature blow up of ρ(T).
H/M (T)andH/M (T),andthereforeH/M (T),are both transitions can be clearly identified in dρ/dT and
ab c ave
indistinguishableintheparamagneticstate. Theinferred d(χ T)/dT.
ave
effective moment, µ = 8.01µ , is in agreement with
eff B
the theoretical prediction for Gd+3 (7.94µ ). The aver-
B
age CW temperature is θ = −26 K, comparable with I. TbPd P
ave 2 2
EuPd P . Both µ and θ are in agreement with
2 2 eff ave
previously reported polycrystalline data [12]. The M(T)/H data of TbPd P (Fig. 10(a)) shows ex-
2 2
In Figure 9(c), the magnetization isotherm at T = tremeaxialanisotropywithχ (cid:29)χ atlowtemperature.
c ab
2.0 K is presented. The M(H) curves of the H (cid:107)ab M (T)/H is monotonically increasing with decreasing
c
and H (cid:107)c directions are isotropic up to H = 10 kOe. temperature. Below 15 K there are 3 clear transitions.
The H (cid:107)ab curve shows a metamagnetic transition at M (T)/H follows a CW law above T > 150 K. Below
ab
H = 14 kOe. At H = 30 kOe, a metamagnetic tran- 150KthereisabroadmaximuminM (T)/H,centered
ab
sition takes place for the H (cid:107)c direction. At the high- around110K,consistentathermaldepopulationofCEF
est applied field of 55 kOe the magnetic moment reaches levels leading to the strong anisotropy.
1.9µB, which is lower than the theoretical value of 7µB The H/M(T) data are plotted in Fig. 10(b). Both
for a free Gd+3 ion. H /M(T) and H/M (T) are linear above 200K with a
ab c
The zero-field, in-plane resistivity, is shown in CW temperatures θ = −107 K and θ = 43 K. An av-
ab c
Fig. 9(d). ρ(T) is metallic down to 20 K, with RRR erageCWtemperatureofθ =−21Kwithaneffective
ave
= 3. At T =10.1±0.3 K an increase in ρ(T) is evident, moment of µ = 9.71µ were inferred for polycrys-
1 eff B
which can be explained by an opening of a superzone talline averaged H/M (T), consistent with the theo-
ave
gap at the AFM transition, followed by a sharp decrease retical value for Tb+3 (9.72µ ).
B
in ρ(T) at T = 7.0±0.3 K. In the inset of Fig. 9(c), The anisotropic magnetization isotherm data were
2
10
0 .2 0
u/mol)00 ..11 05 ( a ) GH =d 1P dk 2OP e2 (M/Hemu/mol)00 ..12 80 0 1 0 2 0 (mment /f.u.)B112 ...050 rmW -1d/dT (cm K)-0000 ....3036 0 T e m5 p e r1a0tu re1 5(K )2 0000 ...123 cd(T)/dTave
m T e m p e ra tu re (K ) o G d P d P
(e M 2 2
M/H0 .0 5 H || c netic0 .5 ( c ) T = 2 H K || c
H || a b g
a H || a b
M
0 .0 0 0 .0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 1 0 2 0 3 0 4 0 5 0
T e m p e r a tu r e ( K ) M a g n e tic F ie ld ( k O e )
5 0
4 0
( b ) ( d )
4 0 G d P d P G d P d P
2 2 ) 2 2
) H = 1 k O e cm3 0 H = 0
u 3 0 m
m h )1 5 .5
(mol/e 2 0 mity (O2 0 Ohm cm111 445 ...050
H/M 1 0 HHA v ||e|| rcaa b g e Resistiv1 0 I || ( a b ) rm (11 33 ..05 0 T5e m p e1 r0a tu r1e 5 (K ) 2 0
0 0
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0 0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
T e m p e r a tu r e ( K ) T e m p e r a tu r e ( K )
FIG. 9: Measurements of GdPd P . (a) Anisotropic M(T)/H measured at H = 1 kOe. Inset: low-temperature blow up
2 2
of M(T)/H. (b) Anisotropic and polycrystalline averaged H/M(T). (c) Anisotropic magnetization isotherm measured at
T = 2.0 K. Inset: low-temperature blow up of dρ/dT and d(χ T)/dT. (d) Zero-field, in-plane resistivity. Inset: low-
ave
temperature blow up of ρ(T).
measuredatT =2.0KandareshowninFig.10(c). The value of the resistivity is rather small, all transitions
M(H)curvefortheH (cid:107)ab directionhasafeaturelesslin- can be clearly identified in the inset. Three transitons,
ear field dependence. In the case of H (cid:107)c direction, sev- T =12.0±0.4K,T =7.5±0.4KandT =4.6±0.4K,
1 2 3
eralmetamagnetictransitionwereobservedintheM(H) canbeinferredfromdρ/dT (insetofFig10(c))andcorre-
curve, where the magnetic moment manifests character- lated with the corresponding anomalies in d(χ T)/dT.
ave
isticstep-likebehavior. Forincreasedfield,threewellde-
finedplateauswithamomentsizeof3µ atH ∼=20kOe,
B
5.5µ atH ∼=60kOeand9µ aboveH ∼=75kOewere
B B J. DyPd P
observed. Thetwolower-fieldtransitionshaveasubstan- 2 2
tial hysteresis, clearly showing they are first order. The
magnetic moment at the last plateau reaches the the- MeasurementsperformedonDyPd2P2aresummarized
oretical saturated moment for Tb+3 (9.00µB), suggest- in Fig. 11. The M(T)/H data of DyPd2P2 (Fig. 11(a))
ing that more meta-magnetic transitions are unlikely at are similar to that of TbPd2P2, but with only two ob-
higher applied magnetic fields. Similarly rich metamag- served magnetic transitions.
netic behavior had been observed in TbNi Ge [27, 32]. Theanisotropicinversemagneticsusceptibilityisplot-
2 2
ted in Fig. 11(b). The CW temperatures inferred in the
The zero-field, in-plane resistivity of TbPd2P2 is plot- paramagnetic state are θab = -37 K, θc = 16 K and θave
ted in Fig. 10(d). The residual resistivity ratio of = -11 K. The effective moment is 10.62 µB, consistent
TbPd2P2 is RRR=2.5. ρ(T) is metallic down to 30 K, with predicted value for Dy3+ (10.64 µB).
with no clear signature for loss of spin-disorder scatter- The anisotropic magnetization isotherms were mea-
ing below the highest transition temperature. A feature sured at T = 2.0 K and are depicted in Fig. 11(c). For
more consistent with an opening of a superzone gap is the H (cid:107)c M(H) curve, two meta-magnetic transitions
observed instead. Although the effect on the absolute were observed. There is a plateau with a moment size of