Study of Structural and Magnetic Properties of Gallium Free Heusler Alloys exhibiting Martensitic

221 Pages·2014·7.05 MB·English

Study of Structural and Magnetic
Properties of Gallium Free Heusler Alloys
exhibiting Martensitic Transitions
A Thesis submitted to Goa University for the Award of the Degree of
DOCTOR OF PHILOSOPHY
in
Physics
By
Dominick Nelson Lobo
Research Guide
Dr. K. R. Priolkar
Goa University
Taleigao Goa
(2014)
DECLARATION
The author hereby declares that this thesis represents work which has been carried out
by him and that it has not been submitted to any other University or Institution for the
award of any Degree, Diploma, Associateship, Fellowship or any other such title.
Place: Taleigao Plateau.
Date : May, 2014 Dominick Nelson Lobo
CERTIFICATE
I hereby certify that the above Declaration of the candidate Mr. Dominick Nelson Lobo
is true and that this thesis represents his independent work.
Dr. K. R. Priolkar
Department of Physics
Goa University, Goa
DEDICATION
This work is dedicated to my dear son Kevin...
Trust in the Lord with all thine heart; and lean not unto thine own understanding.
In all thy ways acknowledge him, and he shall direct thy paths. - Proverbs 3:5,6
Acknowledgement
It is indeed my privilege to thank all those involved directly or indirectly and contributed
to the success of this work.
First and formost, I thank Jesus Christ, my Father God for everything. HIS presence
was my help.
I wish to express my sincere thanks to my supervisor: Dr. K. R. Priolkar, Department
of Physics, Goa University, for the guidance and the freedom to work in my own way. I
am very indebted to him for bringing the best in me and giving me all the encouragement,
vision and teaching me the finer aspects of research. A great friend of mine, is indeed
rare to find.
Financial assistance from CSIR under Project No. 03(1100)/07/EMR II, DST Travel
assistance is gratefully acknowledged.
A big thanks to Principal Fr.(Dr) Walter D’sa for all encouragement and all assistance
given to me to complete my PhD work and specially for permission to undertake study
leave under UGC F.I.P.
I am thankful to Prof. Vasanthacharya, Solid State and Structural Chemistry Unit,
Indian Institute of Science,(SSCU-IISc) Bangalore, Prof. A. K. Nigam, Tata Institute of
Fundamental Research, Mumbai for all the help in carrying out magnetization experi-
ments. My thanks to Director and staff of NCAOR Vasco for their help in carrying out
EDAX measurments.
ProfusethankstoProf. P.R.Sarode, Prof. J.A.E.DesaandProf. R.B.Tangsaliand
the other members of the teaching faculty at the Department of Physics, Goa University
for their valuable help and feedback through out my research work.
A special thanks to Dr. Ramesh Pai, my subject expert for his views and encourage-
ment.
I am also thankful to my colleagues, Mr R.V. Kanekar, Mr Benedict Soares, Mr.
Manoj Salgaonkar and Mr. Pradeep Morajkar for their continuous encouragement and
support. I specially thank my friend from school days, Mr Remigio D’Souza who helped
me a great deal in big ways throughout these five years of research work.
Specialthankstoalltheresearchstudents, speciallyMr. KapilInglefortheircompany
and support.
A note of thanks to the technical and administrative staff of Physics Department, Goa
University for their cooperation during the tenure of my research.
Specialthankstomyfamily, especiallymywifeNancywhohasgoneaboveandbeyond
what women expect of their spouses in support of me. During my years of research at
the University, she has taken over almost all aspects ofmaintaining our home, has been
a stellar parent at all times, and has managed on her own on numerous occasions that
I have travelled to perform experiments both in India and Japan. Without her love and
support, I would not have considered returning to University, let alone had the confidence
to complete my Ph.D degree. I also owe a debt of gratitude to my children Kevin and
Lisa who have always been there for me.
Contents
1 Introduction 1
1.1 Shape Memory Alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Historical Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Phenomena of Phase Transformation . . . . . . . . . . . . . . . . . . . . . 5
1.3.1 Shape Memory Effect . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3.2 Pseudoelasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
1.3.3 Superelasticity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4 Magnetic Shape Memory Alloys . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4.1 Ni-Mn based FSMAs . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.4.2 Crystal Structure: Structure-Austenite and Martensite . . . . . . . 15
1.4.3 Important Properties of Magnetic Shape Memory alloys . . . . . . . 19
1.4.4 Factors affecting martensitic transformation of MSMA . . . . . . . 25
1.4.5 Magnetic Interaction between constitutent atoms in MSMA . . . . 33
1.5 Aim of the thesis - Motivation for the current research work . . . . . . . . 35
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
i
2 Experimental Techniques 53
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.2 Sample Preparation Technique . . . . . . . . . . . . . . . . . . . . . . . . . 54
2.3 X-ray Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
2.4 Four Probe Resistivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
2.5 Differential scanning calorimetry . . . . . . . . . . . . . . . . . . . . . . . . 57
2.6 Magnetometery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
2.6.1 SQUID Magnetometery . . . . . . . . . . . . . . . . . . . . . . . . 59
2.7 Energy-dispersive X-ray absorption spectroscopy . . . . . . . . . . . . . . . 63
2.8 X-ray Absorption Fine Structure Spectroscopy . . . . . . . . . . . . . . . . 64
2.8.1 Experimental Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
2.8.2 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
2.8.3 Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
2.9 X-ray magnetic circular dichroism (XMCD) . . . . . . . . . . . . . . . . . 77
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
3 Factors influencing martensitic transformation in Ni Mn Z ferro-
2 1+x 1−x
magnetic shape memory alloys 87
3.0.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
3.0.2 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 89
3.0.3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
ii
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
4 Importance of Ni-Mn hybridization in magnetic properties of marten-
sitic state 113
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
4.2 Mn L and Ni L XAS studies . . . . . . . . . . . . . . . . . . . . . . . 115
2,3 2,3
4.3 XMCD Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
4.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
4.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
5 Effect of Fe substitution on martensitic and magnetic properties of Ni-
Mn-In shape memory alloys 131
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
5.2 Ni MnIn Fe alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
2 1−x x
5.3 Ni Mn In Fe and Ni Mn In Fe alloys . . . . . . . . . . . . . . . 139
2 1.5 0.5−y y 2 1.6 0.4−y y
5.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
5.5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
6 Magnetic interactions in the Martensitic phase of ferrimagnetic
Mn NiIn type shape memory alloys 150
2
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
6.2 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
iii
6.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
7 Ab-initio calculations: Determination of Structure of Mn NiIn alloys 166
2
7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
7.2 Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
7.3 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
7.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
8 Summary and Future Work 193
8.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
8.2 Future Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
iv
List of Tables
1.1 Classification of Heusler alloys based on composition, magnetic order and
crystal structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 EDX compositions, T ,and M , M , A and A of Ni Mn In alloys
C S f S f 2 1+x 1−x
determined from magnetization measurements and structure from XRD . . 94
3.2 Bond distances obtained from analysis of Ni and Mn K edge EXAFS in
Ni Mn In alloys. The numbers in parenthesis indicate uncertainty in
2 1+x 1−x
the last digit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
3.3 Results of the fits to the Ni and Mn edge EXAFS data for Ni MnIn. R
2
refers to the bond length and σ2 is the thermal mean-square variation in
the bond length. The fittings were carried out in the k range: 2 – 15 ˚A−1
with k weight = 3 and R range 1– 3 ˚A for Ni K edge and 1 – 5 ˚A for Mn
K edge. Figures in parentheses indicate uncertainty in the last digit. . . . . 103
v
3.4 Results of the fits to the Ni and Mn edge EXAFS data for Ni Mn In .
2 1.4 0.6
R refers to the bond length and σ2 is the thermal mean-square variation in
the bond length. The fittings were carried out in the k range: 2 - 15 ˚A−1
with k weight = 3 and R range 1 - 3 ˚A for Ni K edge and 1 - 5 ˚A for Mn
k edge. Figures in parentheses indicate uncertainty in the last digit. . . . . 104
5.1 Table of percentage of cubic and tetragonal phases and lattice parameters . 137
5.2 Bond distances obtained from analysis of Ni and Mn K edge EXAFS in
Ni MnIn Fe alloys for cubic phase. The numbers in parenthesis indi-
2 1+x 1−x
cate uncertainty in the last digit. . . . . . . . . . . . . . . . . . . . . . . . 139
5.3 Bond distances obtained from XRD of Ni MnIn Fe alloys for tetrag-
2 1+x 1−x
onal and cubic phase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6.1 Values of e/a, T , T and TM for Mn Ni In and Mn Ni In
C M C 2 1+x 1−x 2−y 1.6+y 0.4
alloys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
7.1 Theoratical bond distances of Mn Ni In (cubic phase) based on
2 1.5 0.5
MODEL A and MODEL B (without local structural distortion). . . . . . . 186
7.2 Bond distances obtained from analysis of Ni and Mn K edge EXAFS in
Mn MnIn type alloys.The numbers in brackets indicate the uncertainity in
2
the last digit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
vi