Alloys and Compounds of d-Elements with Main Group Elements. Part 1

369 Pages·1999·6.6 MB·English

by  Y. Nakai

Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 1
1 Magnetic properties of 3d, 4d, and 5d elements,
alloys and compounds
1.1 - 1.4 See Subvolume III/32A
1.5 Alloys and compounds of 3d elements with main group elements
1.5.1 3d elements with Cu, Ag or Au
1.5.1.1 Introduction
General remarks
In this subsection, experimental data for alloys with 3d transition elements (V, Cr, Mn, Fe, Co and
Ni) and noble metals (Cu, Ag, Au) are compiled. These data were published in the period between
1983 and 1994. Data published before 1983 were filed in Landolt-Börnstein New Series, vol. III/19B
edited by G. Zibold. Some data published in 1983 and 1984 were already referred by the previous
editor. These data were omitted to avoid the duplication. For the compilation of data, we followed
the policy of previous editor. Thus, amorphous systems, thin films, ultra-fine particles and
precipitates, which are the fields growing very rapidly, are not treated in this subsection. The ordered
alloys and ternary alloys are filed at the end of the subsection. The atomic short range order is
referred only when it seems to have a significant relation with the magnetism of the alloys.
1.5.1.2 Definition of various kinds of magnetism
1.5.1.2.1 Spin glass, cluster glass, mictomagnetism and reentrant spin glass
The most of data published in this period in the field of the subsection are concerned with spin
glasses. Spin glass in a wide sense is usually used for the system with strong viscous magnetism
below a characteristic temperature T (freezing temperature) but without any magnetic long range
f
order. In a narrow sense, it is used especially for the dilute alloys which can be approximately
considered to have a random distribution of the magnetic components. Some authors use cluster glass
or mictomagnetism for the system with higher concentration ( > few at% ) of magnetic component.
Except for T, however, physical properties (the cusp shaped anomaly in the susceptibility, a broad
f
distribution of relaxation time and so on) are not sensitive to the concentration of the magnetic
component.
Reentrant spin glass also shows the viscous magnetism below the characteristic temperature T,
f
but above it, long range magnetic order (ferromagnetism or antiferromagnetism) is observed. Actual
microscopic spin configurations of both high temperature phase and reentrant spin glass phase are
still controversial.
Many experimental results for spin glasses, together with the theories, are reviewed in [83f1,
85f1, 86b1, 88m1, 88m2, 91f1].
Landolt-Börnstein
New Series III/32B
2 1.5.1 3d elements with Cu, Ag or Au: introductory remarks [Ref. p. 105
1.5.1.2.2 Diamagnetism
Diamagnetism is known as a system which shows a negative susceptibility of the order of - 10- 5 to
the applied magnetic field. The response is temperature independent. The origin of diamagnetism is
an orbital motion of electrons around the nuclei, induced electromagnetically by the applied field.
1.5.1.2.3 Paramagnetism
If the temperature is high enough to exceed the coupling energy between magnetic moments, the
orientation of each moment rotates freely due to the thermal agitation. This is a paramagnetic state.
The susceptibility of paramagnetism is an order of 10- 3…10- 6 and inversely proportional to the
absolute temperature (K). Pauli paramagnetism comes from the excitation of conduction electrons in
metallic system and shows a temperature independent susceptibility.
Superparamagnetism is used for magnetic particles or clusters, inside of which magnetic order
develops, but total ordered moment of each particle (cluster) rotates freely by thermal energy. An
assembly of magnetic particles (clusters) with various particle sizes shows similar behaviors in the
susceptibility to that of cluster glass.
1.5.1.2.4 Ferromagnetism
In a ferromagnet a spontaneous magnetization exists, i.e., the magnetic moments are aligned parallel
to one another without applied magnetic field. This is due to the positive exchange interaction
between neighbouring spins. The spontaneous magnetization decreases with increasing temperature
and becomes zero at the Curie temperature T . Above T it behaves as the paramagnet and the
C C
susceptibility obeys a Curie-Weiss law.
1.5.1.2.5 Antiferromagnetism
In an antiferromagnet the magnetization is completely cancelled. The magnetic lattices are separated
into sublattices. The magnetic moments in each sublattice are aligned parallel to one another but total
magnetization is zero due to the cancellation of the magnetic moments between different sublattices.
The susceptibility is small and positive. The susceptibility as a function of temperature shows a
maximum at the ordering temperature (Néel temperature) T .
N
A period of magnetic order is not always commensurate with the lattice period. A spin density
wave (SDW) has an incommensurate spin alignment with a wave vector which is determined by the
Fermi surfaces of conduction electrons.
1.5.1.2.6 Ferrimagnetism
In a ferrimagnet magnetizations between sublattices with antiparallel coupling are not cancelled and
behave almost like the ferromagnet below the ordering temperature T .
N
1.5.1.2.7 Metamagnetism
Metamagnetism is a magnetically ordered state which shows zero magnetization under the zero
magnetic field but abrupt increasing of magnetization at the certain magnetic field. The hysteresis for
the change of magnetic field is small.
Landolt-Börnstein
New Series III/32B
Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 3
1.5.1.3 Some remarks on magnetization
1.5.1.3.1 Spontaneous magnetization
In a ferromagnet, magnetic moments coupling with the positive exchange interaction are aligned
parallel to one another at temperature below T and the spontaneous magnetization results without
C
external magnetic field.
1.5.1.3.2 Saturation magnetization
A bulk ferromagnet is divided into many ferromagnetic domains under zero magnetic field and total
magnetization is far smaller than the spontaneous magnetization. The magnetization however reaches
to the saturated value under rather weak applied field due to the realignment of magnetic domains.
This is called a saturation magnetization.
1.5.1.3.3 Thermoremanent magnetization (TRM)
A thermoremanent magnetization is observed when a spin glass sample is cooled down through T
f
under certain magnetic field, then the magnetization is measured after removing the magnetic field.
1.5.1.3.4 Isothermal remanent magnetization (IRM)
An isothermal remanent magnetization is measured below T for the spin glass sample cooled down
f
under zero magnetic field.
1.5.1.3.5 Wait time effect in spin glass
The spin glass has a strong magnetic viscousity and the relaxation time of the magnetization
distributes continuously from atomic time scales to macroscopic time scales. A spin glass sample is
cooled down from a reference temperature above T to the measurement temperature T (below T )
f m f
in the zero magnetic field. At T the sample is kept at constant temperature for a certain wait time t
m w
before the external field is applied, then the time development of the IRM is measured in a constant
magnetic field. The IRM shows a striking wait time dependence (Fig. 43). The same kind of wait
time effect can be observed for the TRM.
1.5.1.3.6 Magnetic anisotropy
In actual magnetic substances the internal energy depends on the direction of spontaneous
magnetization. Generally the magnetic anisotropy is a reflection of crystal symmetry of the sample
and is called a magnetocrystalline anisotropy. Another type of anisotropy is an induced magnetic
anisotropy which is induced by some treatment such as field cooling, cold working or neutron
irradiation. Anisotropy energy is usually expressed in the form of an anisotropy constant K times an
angular dependence. An axial anisotropy has a p symmetry and an easy axis is parallel to one of
crystal axes. Directional anisotropy is independent from crystal axes and has a 2p symmetry. The
Dzyaloshinsky-Moriya interaction causes the directional anisotropy.
Landolt-Börnstein
New Series III/32B
4 1.5.1 3d elements with Cu, Ag or Au: introductory remarks [Ref. p. 105
1.5.1.4 Remarks on the data analysis
1.5.1.4.1 Curie-Weiss law
The susceptibility of paramagnetic substance is described as
m Np2
c (T)= 0 eff (1)
3k (T- Q )
B
where N is number of magnetic atoms per unit mass, Q is the paramagnetic Curie temperature and
p shows the effective magnetic moment. The effective moment and the paramagnetic Curie
eff
temperature are deduced by a plot of c –1(T) versus T as the slope of straight line and its intercept
with abscissa, respectively. The effective moment is related to the total angular momentum J = L + S
as
p2 =g2J(J+1)m 2 (2)
eff B
with the Landé g-factor.
1.5.1.4.2 Arrott plot
Above the Curie temperature, the magnetization for ferromagnetic substance approximately obeys
the equation
H T- T M
( )= C +( )2 (3)
M T M
1 1
where M and T are constants. This is a result of the mean field approximation. Arrott plots are
1 1
isotherm of H/M versus M2 plot and parallel straight lines are obtained for each temperature. The
Curie temperature T is determined by the straight line which passes through the origin.
C
1.5.1.5 High frequency properties
The time development of spin configuration is a fundamental aspect to understand the microscopic
picture of the spin glasses. Since various experimental techniques have each characteristic frequency,
experimental data obtained by different techniques give us the information of the system in different
time scale.
1.5.1.5.1 Neutron scattering
The characteristic frequency of neutron diffraction is typically about 10- 10(cid:1)10- 11 s. The fastest
motion of spins is measurable as inelastic scattering of neutrons (Fig. 21). The spin dynamics slower
than this time scale is observed as elastic scattering (Fig. 20). The freezing temperature of spin glass
studied by neutron elastic scattering is always higher than that determined from the cusp in the
susceptibility or the disappearance of hyperfine field in Mössbauer spectroscopy (Fig. 32).
1.5.1.5.2 NMR and Mössbauer spectroscopy (ME)
Both techniques enable the measurement of the hyperfine magnetic field at the nuclear position. In
spin glass system, the finite value of hyperfine field is usually observed below T. The lifetime of the
f
Landolt-Börnstein
New Series III/32B
Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 5
excited nuclear level in typical ME absorber Fe57 is 1(cid:215)10- 7 s. The spin dynamics faster than this time
scale is observed as a paramagnetic component [85M3]. For ferromagnetic substances, the NMR
signal is enhanced by the displacement of domain walls driven by the external rf-field.
1.5.1.5.3 mmmm SR
In the muon spin relaxation technique, the polarized muons with positive charge are shot into the
sample. When the muon, which is trapped at the interstitial site of the sample, decays into positron
after a lifetime of 2.2 m s, the information of local magnetic field is recorded as a depolarization of
the muon spin. Thus the characteristic frequency of m SR is 10- 6 s. With this technique, the transition
to the spin glass phase and dynamics in this phase can be studied (Figs. 69-78).
1.5.1.5.4 ESR
ESR probes the local magnetic moment through the magnetization of conduction electrons. In spin
glasses, remarkable increases of the linewidth W and the resonance shift d H are observed around T
res f
and these enlargements are frequency dependent (Fig. 140).
1.5.1.5.5 Perturbed angular correlation (PAC)
PAC spectroscopy observes the hyperfine field through the nuclear spin precession in the time scale
determined by the lifetime of the probe (» 10- 7…10- 8 s). After the emission of first g -ray, nuclear
spin in the intermediate state interacts with an electromagnetic field and precesses, causing the
angular correlation of the second g -ray emission to change. From PAC spectroscopy data, the
temperature dependence of hyperfine field and the distribution of local magnetic field in spin glasses
are discussed (Fig. 59).
1.5.1.6 Hall resistivity
Hall resistivity in noble metal with dilute magnetic impurities is expressed as
r H = R0B + RHM (4)
where B and M indicate the magnetic induction and the magnetization, respectively. The first term is
an ordinary Hall effect and is associate with the Lorentz force for noble metals. The second term is
called the extraordinary or anomalous Hall resistivity and shows the orbital contribution to the local
impurity moments. The anomalous Hall coefficient (R ) which includes the information about the
H
orbital susceptibility is compared with the susceptibility data for spin glasses (Fig. 209).
1.5.1.7 Remarks on some concepts of metallurgy
Magnetic properties of alloys depend not only on the concentration of magnetic atoms but also on
their spacial arragement. In an ideal spin glass, a random distribution of magnetic atoms is assumed.
Most of spin glass theories are based on this assumption but in actual substances, it is difficult to
produce random alloys. The spacial distribution of magnetic atoms in alloys can be partly controlled
by the appropriate thermal treatment.
Landolt-Börnstein
New Series III/32B
Ref. p. 105] 1.5.1 3d elements with Cu, Ag or Au: introductory remarks 5
excited nuclear level in typical ME absorber Fe57 is 1(cid:215)10- 7 s. The spin dynamics faster than this time
scale is observed as a paramagnetic component [85M3]. For ferromagnetic substances, the NMR
signal is enhanced by the displacement of domain walls driven by the external rf-field.
1.5.1.5.3 mmmm SR
In the muon spin relaxation technique, the polarized muons with positive charge are shot into the
sample. When the muon, which is trapped at the interstitial site of the sample, decays into positron
after a lifetime of 2.2 m s, the information of local magnetic field is recorded as a depolarization of
the muon spin. Thus the characteristic frequency of m SR is 10- 6 s. With this technique, the transition
to the spin glass phase and dynamics in this phase can be studied (Figs. 69-78).
1.5.1.5.4 ESR
ESR probes the local magnetic moment through the magnetization of conduction electrons. In spin
glasses, remarkable increases of the linewidth W and the resonance shift d H are observed around T
res f
and these enlargements are frequency dependent (Fig. 140).
1.5.1.5.5 Perturbed angular correlation (PAC)
PAC spectroscopy observes the hyperfine field through the nuclear spin precession in the time scale
determined by the lifetime of the probe (» 10- 7…10- 8 s). After the emission of first g -ray, nuclear
spin in the intermediate state interacts with an electromagnetic field and precesses, causing the
angular correlation of the second g -ray emission to change. From PAC spectroscopy data, the
temperature dependence of hyperfine field and the distribution of local magnetic field in spin glasses
are discussed (Fig. 59).
1.5.1.6 Hall resistivity
Hall resistivity in noble metal with dilute magnetic impurities is expressed as
r H = R0B + RHM (4)
where B and M indicate the magnetic induction and the magnetization, respectively. The first term is
an ordinary Hall effect and is associate with the Lorentz force for noble metals. The second term is
called the extraordinary or anomalous Hall resistivity and shows the orbital contribution to the local
impurity moments. The anomalous Hall coefficient (R ) which includes the information about the
H
orbital susceptibility is compared with the susceptibility data for spin glasses (Fig. 209).
1.5.1.7 Remarks on some concepts of metallurgy
Magnetic properties of alloys depend not only on the concentration of magnetic atoms but also on
their spacial arragement. In an ideal spin glass, a random distribution of magnetic atoms is assumed.
Most of spin glass theories are based on this assumption but in actual substances, it is difficult to
produce random alloys. The spacial distribution of magnetic atoms in alloys can be partly controlled
by the appropriate thermal treatment.
Landolt-Börnstein
New Series III/32B
6 1.5.1 3d elements with Cu, Ag or Au: introductory remarks [Ref. p. 105
1.5.1.7.1 Quenching
The structural characteristic at high temperature can be more or less retained by cooling the sample
very rapidly (quenching). If the measurement temperature is not high enough for atoms to diffuse in
the sample, quenched state would be retained as an unstable state. An atomic diffusion constant,
however, is function of temperature, density of defects, atomic sizes, and so on, and these values
vary from systems to systems. It depends on the alloy systems whether the rapid quenching is
effective or not.
1.5.1.7.2 Annealing, ageing
Heating a sample to high temperature and keeping it for a certain period in order to promote an
atomic diffusion is reffered to as annealing. Annealing is carried out for various purposes; to
homogenize the composition, to grow the precipitates or the atomic short range order, to relax the
strain introduced by the treatment on preparing the specimen. Ageing corresponds to annealing at
comparatively low temperature and for long period.
1.5.1.7.3 Cold working, plastic deformation
Cold working or plastic deformation deforms the shape of the sample macroscopically and introduce
many atomic defects and dislocations. These are considered to cause decreases in the average
magnetic moment and the atomic short range order.
Landolt-Börnstein
New Series III/32B
Ref. p. 105] 1.5.1.8 Survey 3d elements with Cu 7
1.5.1.8 Surveys
Survey 1. Binary 3d- Cu alloys. Numbers in italic and roman refer to tables and figures, respectively.
For ternary alloys containg Cu, see Survey 4.
Alloy Mn- Cu Fe- Cu Co- Cu Ni- Cu
Magnetic structure 15-20, 22
Magnetic phase diagram 11-14 104, 105 114
Transition temperature
Magnetic susceptibility 7, 106, 107 118
Critical exponent 3
Paramagnetic properties
Curie-Weiss law 24
p 4
eff
Q 4
Spin-glass, and mictomagnetic
properties
susceptibility 9, 23, 25-31, 42, 115
71, 74
T 1, 2 105 9
f
M, IRM, TRM, M(t) 34-41, 43, 47-50 116
magnetic cluster 33
hysteresis 44, 86
anisotropy 45, 46, 52 109, 110
Ferromagnetic properties
T 9
C
M, M
0
Arrott plot
hysteresis
anisotropy
Antiferromagnetic properties
T
N
susceptibility 23
High-frequency properties
neutron scattering 5, 21, 32, 33, 71, 73 10, 117
NMR 2, 53-58
Mössbauer 111
m SR 69-78
PAC 59 7
ESR 10, 60-68
Transport properties 87-97 113 120
Magneto-mechanical properties 79
Heat properties 51, 80-86
Landolt-Börnstein
New Series III/32B
8 1.5.1.8 Survey 3d elements with Ag [Ref. p. 105
Survey 2. Binary 3d- Ag alloys. Numbers in italic and roman refer to tables and figures,
respectively. For ternary alloys containg Ag, see Survey 4.
Alloy Mn- Ag Fe- Ag
Magnetic structure 22, 125
Magnetic phase diagram 6, 124
Transition temperature
Magnetic susceptibility
Critical exponent 3 7
Paramagnetic properties
Curie-Weiss law 11, 126
p 11
eff
Q 11
Spin-glass and mictomagnetic
properties
susceptibility 8 ,9, 127, 128
T 1, 1
f
M, IRM, TRM, M(t) 129-133
magnetic cluster
hysteresis
anisotropy 134
Ferromagnetic properties
T
C
M, M
0
Arrott plot
hysteresis
anisotropy
Antiferromagnetic properties
T
N
susceptibility
High-frequency properties
neutron scattering
NMR 2, 135
Mössbauer
m SR 142, 143
PAC 7
ESR 10, 136-141
Transport properties 144
Magneto-mechanical properties
Heat properties
Landolt-Börnstein
New Series III/32B
Ref. p. 105] 1.5.1.8 Survey 3d elements with Au 9
Survey 3. Binary 3d- Au alloys. Numbers in italic and roman refer to tables and figures,
respectively. For ternary alloys containg Au, see Survey 4.
Alloy V- Au Cr- Au Mn- Au MnAu Mn Au
4 2 5
Magnetic structure
Magnetic phase diagram 148
Transition temperature
Magnetic susceptibility 146
Critical exponent
Paramagnetic properties
Curie-Weiss law
p 145 13
eff
Q 13
Spin-glass and mictomagnetic
properties
susceptibility 152
T 1, 13, 2
f
M, IRM, TRM, M(t) 149 153
magnetic cluster
hysteresis
anisotropy
Ferromagnetic properties
T 14
C
M, M
0
Arrott plot
hysteresis
anisotropy
Antiferromagnetic properties
T 14
N
susceptibility
High-frequency properties
neutron scattering 73
NMR 2
Mössbauer
m SR 73, 76, 78
PAC
ESR
Transport properties 147 154-156
Magneto-mechanical properties 14 14
Heat properties 14, 157 14, 157
Landolt-Börnstein
New Series III/32B