submitted mohammed anwar hossain

149 Pages·2016·6.46 MB·English

INFLUENCE OF Gd SUBSTITUTION ON STRUCTURAL AND
MAGNETIC PROPERTIES OF Co Cu Zn Gd Fe O
0.40 0.20 0.40 x 2-x 4

A Dissertation Submitted to the Department of Physics, Bangladesh University of
Engineering & Technology, Dhaka, in Partial Fulfillment of the Requirement for
the Degree of Master of Philosophy in Physics

SUBMITTED
By
MOHAMMED ANWAR HOSSAIN

Examination Roll No. : 0411143004P
Session : April 2011

DEPARTMENT OF PHYSICS
BANGLADESH UNIVERSITY OF ENGINEERING & TECHNOLOGY
DHAKA 1000, BANGLADESH
CANDIDATE’S DECLARATION

It is hereby declared that this thesis or any part of it has not been submitted
elsewhere for the award of any degree or diploma.

Mohammed Anwar Hossain

II

DEDICATED TO
MY FATHER
MOHAMMED ABUL BASHAR
AND
MY BELOVED MOTHER
ANWARA BEGUM

IV
ACKNOWLEDGEMENTS

First of all I express all my admiration and devotion to the almighty Allah, the most
beneficent who has enabled me to perform this research work and to submit this thesis.
I express my profound gratitude to my honorable supervisor Prof. Dr. A.K.M. Akther
Hossain, Department of Physics, Bangladesh University of Engineering and Technology (BUET),
for his constant direction, constructive criticism and inspiration in pursuing the whole
investigation of the present research. Words are always insufficient to express his working
capacities and unending enthusiasm for scientific rigorousness for innovative investigations. This
always becomes the everlasting source of inspiration for his students.
I am very grateful to Prof. Fahima Khanam, Head, Department of Physics, BUET,
Dhaka, Bangladesh, for giving me all sorts of supports from the Department.I like to express my
gratitude to Prof. Dr. Md. Abu Hashan Bhuiyan, Prof. Dr. Jiban Podder, Prof. Dr. Md. Feroz
Alam Khan, Prof. Dr. Md. Mostak Hossain, Prof. Dr. Afia Begum, Prof. Dr. Md. Forhad Mina,
Prof. Dr. Md. Rafi Uddin, Dr. Nasreen Akter, Dr. Mohammad Abdul Basith, Dr. Mohammad
Abu Sayem Karal and all other teachers of the Department of Physics, for their cooperation.
I would like to thank Dr. Nazrul Islam Khan, Principal Scientific Officer, Materials
Science Division, Atomic Energy Commission, Dhaka, Bangladesh, for giving me all sorts of
supports to measure the XRD analysis of my various samples.
I am also grateful to Dr. Farhad Alam Dr. Md. Belal Hossain, Dr. Sajal Chandra
Mazumder & Dr. Mohammad Julhash Miah, for their inspiration and encouragement. I wish to
give special thanks to PhD researchers of the Department of Physics, Abdulla Al-Momin, Md.
Kamrul Haque Bhuiyan, Bablu Chandra Das & Roksana pervin for their constant support. I also
gratefully acknowledge the wishes to M.Phil. Research fellows, Md. Nazrul Islam, Mamun-Ar-
Rashid, Abdul Ahad, Md. Arifur Rahman, Sonnet Kumar, and all others researchers of
Experimental Solid State Physics Lab, BUET, for their cooperation throughout the study.
I remember with much gratefulness Honorable Planning Minister Lotus Kamal, Md.
Ibrahim Khalil Mozumder and other members of GB, Principal Md. Zakir Hossain, Maolana
Lokman Hakim & all respected teachers of Choto Sarifpur Degree College for their valuable
suggestions and inspiration.
Finally, I would mention a very special gratefulness for the moral support and sustaining
inspiration provided by the members of my family. This dissertation would never have been
possible without their love and affection.
(Mohammed Anwar Hossain)

Author
V
ABSTRACT
Polycrystalline Co Cu Zn Gd Fe O prepared by standard solid state
0.40 0.20 0.40 x 2-x 4
reaction technique sintered at various temperatures (1000, 1050, 1100 and 1150ºC) in
air for 3 hours. Structural, surface morphology and compositional analysis are
characterized by X-ray diffraction (XRD) and Scanning electron microscopy (SEM)
respectively. The DC magnetizations as a function of applied magnetic field are
performed and increases with increasing applied magnetic field up to 0.1T, then
saturation occurs. The XRD patterns confirm the formation of spinel structure. The
lattice parameter, a , increases with the Gd content. The bulk density (ρ ) increases
o B
and porosity (p) of the samples decreases with the increase of Gd content. The
average grain size increases with the Gd content, then decreases. The initial
permeability (µ/) is found to increase with Gd content up to x=0.050 and then
i
decreases. The value of Q-factor increases with increasing Gd contents from x=0.000
to x=0.050, then it decreases. The real part of dielectric constant (ε/) initially decreases
rapidly in the low frequency region but at very high frequencies its value becomes so
small that it becomes independent of applied frequency. The dielectric loss tangent
(tanδ ) decreases with the increase of Gd content due to the decrease of polarization.
E
The value of electric modulus (M/) is very low in the low frequency region. As
frequency increases the value of M/ increases and reaches a maximum constant value.
The value of Z/ (real part of impedance) and Z// (imaginary part impedance) decrease
with increasing frequency. The decrease in the values of Z/ and Z// shows that the ac
conductivity increases as the frequency increases and Z/ indicates dielectric relaxation
process. The value of AC conductivity (ζ ) increases with AC applied field which
AC
obeys the Jonschers power law.
VI
CONTENTS
ACKNOWLEDGEMENTS V
ABSTRACT VI
CONTENTS VII
LIST OF FIGURES XI
LIST OF TABLES XVII
LIST OF SYMBOLS AND ABBREVIATIONS XVIII

CHAPTER 1
INTRODUCTION 1-8
1.1 Background and present state of the problem 1
1.2 Motivation of this Research 3
1.3 Objectives with specific aims 5
1.4 Outline of the Thesis 6
References 7

CHAPTER 2
THEORETICAL BACKGROUND 9-57
2.1 Overview of the materials 9
2.2 Magnetic ordering 15
2.3 Crystal Structure of Spinel Ferrites 18
2.3.1 Ionic Charge Balance and Crystal Structure of Cubic Spinel Ferrite 18
2.3.2 Site Preferences of the Ions 21
VII
2.3.3 Unit Cell Dimensions 22
2.4 Cation Distribution of Spinel Ferrites 23
2.5 Interaction between Magnetic Moments on Lattice Sites 25
2.6 Magnetism in Spinel Ferrite 27
2.6.1 Magnetic Moments of Some Spinel Ferrites 28
2.6.1.1 Inverse Spinel 28
2.6. 2 Exchange Interactions in Spinel 29
2.6.3 Néel Theory of Ferrimagnetism 32
2.7 Microstructure 37
2.8 Theories of Permeability 39
2.8.1 Mechanisms of Permeability 41
2.8.1.1 Wall Permeability 41
2.8.1.2 Rotational Permeability 43
2.8.1.3 Frequency dependent Permeability Curve 45
2.9 Magnetization Mechanism 48
2.9.1 Concept of Magnetic Domain and Domain Wall 48
2.9.2 The dynamic behavior of Domains 50
2.9.3 Bulk Material Magnetization 51
2.9.4 The Magnetization Curve 52
References 54

CHAPTER 3
SAMPLE PREPARATION 58-62
3.1 Composition of the studied ferrite system 58
VIII
3.2 Sample preparation techniques 58
3.2.1 Material synthesis and sample preparation 59
3.2.2 Solid state reaction 59
3.2.3 Calcination and sintering 60
3.3 Preparation of the present samples 61
References 62

CHAPTER 4
EXPERIMENTAL TECHNIQUES 63-80
4.1 X-ray diffraction 63
4.1.1 Phillips X′ Pert PRO X-ray diffractometer 65
4.1.2 Powder X-ray diffractometer 66
4. 2 Surface morphology and microstructure 67
4.3 Scanning Electron Microscope (SEM) 67
4.3.1 Scanning process and image formation 68
4.4 Complex permeability measurement 70
4.5 Frequency characteristics of the present samples 70
4.6 Transport properties 72
4.6.1 Dielectric Constant 72
4.6.2 Dielectric Loss 73
4.6.3 Impedance spectroscopy 75
4.6.4 Modulus spectroscopy 76
4.7 DC magnetization measurement 77
4.7.1 Vibrating Sample Magnetometer (Micro Sense, EV9) 78
IX
4.7.2 Working principle of VSM 78
References 80
CHAPTER 5
RESULTS AND DISCUSSION 81-125
5.1 XRD analysis of the polycrystalline Co Cu Zn Gd Fe O 81
0.4 0.2 0.4 x 2-x 4
5.2 Lattice Constants of the polycrystalline Co Cu Zn Gd Fe O 82
0.4 0.2 0.4 x 2-x 4
5.3 Density and porosity of the polycrystalline Co Cu Zn Gd Fe O 85
0.4 0.2 0.4 x 2-x 4
5.4 Microstructures of Co Cu Zn Gd Fe O 88
0.40 0.20 0.40 x 2-x 4
5.5 Frequency dependence of complex permeability 96
5.6 Relative quality factor 103
5.7 Frequency dependence of loss factor 106
5.8 DC magnetization Co Cu Zn Gd Fe O 107
0.40 0.20 0.40 x 2-x 4
5.9 Dielectric study 111
5.10 Modulus study 114
5.11 Impedance study 117
5.12 AC conductivity study 120
References 122

CHAPTER 6
CONCLUSIONS 126-130
6.1 Conclusions 126
6.2 Suggestions for future work 130

X