Luận văn Study of perpendicular exchange bias mechanism in MnPd/Co multilayers

CONTENTS Preface 1 Chapter 1 Introduction 1.1 Background 31.2 Overview on exchange bias 6 1.3 Previous studies on perpendicular exchange bias 12 Chapter 2 Experimental 2.1 Introduction 152.2 Sample preparation 15 2.3 Experimental techniques 18 2.3.1 Glancing incident X-ray diffraction 18 2.3.2 Field emission scanning electron microscope 18 2.3.3 Stylus-method profilemetry 19 2.3.4 Energy dispersive X-ray spectrometer 19 2.3.5 Wavelength dispersive X-ray spectrometer 20 2.3.6 Magnetization hysteresis loops 21 2.3.7 Magnetization – temperature curve 22 2.3.8 Magnetic force microscope & atomic force microscope 22 Chapter 3 Experimental results 3.1 Introduction 233.2 Crystallographic structure 23 3.2.1 Glancing incident X-ray diffraction 23 3.2.2 Cross-section observation 25 3.3 Magnetic properties 25 3.3.1 Domain observation 26 3.3.2 Magnetization hysteresis loops at low temperature 26 3.3.3 Magnetization hysteresis loops at room temperature 30 3.3.4 Temperature dependence of magnetization in MnPd/Co multilayers 36Chapter 4 Discussions 4.1 Introduction 374.2 Crystallographic structure 37 4.2.1 Glancing incident X-ray diffraction 37 4.2.2 Cross-section observation 38 4.3 Magnetic properties 38 4.3.1 Domain observation 39 4.3.2 Thickness dependence of exchange bias 39 4.3.2.1 Co thickness dependence of exchange bias 39 4.3.2.2 MnPd thickness dependence of exchange bias 41 4.3.3 Perpendicular magnetic anisotropy in MnPd/Co multilayers 434.3.3.1. Perpendicular anisotropy at low temperature 44 4.3.3.2. Perpendicular anisotropy at roomtemperature 46 4.3.3.3. Effect of annealing on perpendicular anisotropy 46 4.3.3.4. Anomalous field induced anisotropy 50 4.3.4 Temperature dependence of magnetization in MnPd/Co multilayers 514.4 Explanation of exchange bias coupling mechanism 52 Conclusions and further direction 56References 58

CONTENTS

Preface 1

Chapter 1 Introduction

1.1 Background 3

1.2 Overview on exchange bias 6

1.3 Previous studies on perpendicular exchange bias 12

Chapter 2 Experimental

2.1 Introduction 15

2.2 Sample preparation 15

2.3 Experimental techniques 18

2.3.1 Glancing incident X-ray diffraction 18

2.3.2 Field emission scanning electron microscope 18

2.3.3 Stylus-method profilemetry 19

2.3.4 Energy dispersive X-ray spectrometer 19

2.3.5 Wavelength dispersive X-ray spectrometer 20

2.3.6 Magnetization hysteresis loops 21

2.3.7 Magnetization – temperature curve 22

2.3.8 Magnetic force microscope & atomic force microscope 22

Chapter 3 Experimental results

3.1 Introduction 23

3.2 Crystallographic structure 23

3.2.1 Glancing incident X-ray diffraction 23

3.2.2 Cross-section observation 25

3.3 Magnetic properties 25

3.3.1 Domain observation 26

3.3.2 Magnetization hysteresis loops at low temperature 26

3.3.3 Magnetization hysteresis loops at room temperature 30

3.3.4 Temperature dependence of magnetization in MnPd/Co multilayers 36

Chapter 4 Discussions

4.1 Introduction 37

4.2 Crystallographic structure 37

4.2.1 Glancing incident X-ray diffraction 37

4.2.2 Cross-section observation 38

4.3 Magnetic properties 38

4.3.1 Domain observation 39

4.3.2 Thickness dependence of exchange bias 39

4.3.2.1 Co thickness dependence of exchange bias 39

4.3.2.2 MnPd thickness dependence of exchange bias 41

4.3.3 Perpendicular magnetic anisotropy in MnPd/Co multilayers 43

4.3.3.1. Perpendicular anisotropy at low temperature 44

4.3.3.2. Perpendicular anisotropy at roomtemperature 46

4.3.3.3. Effect of annealing on perpendicular anisotropy 46

4.3.3.4. Anomalous field induced anisotropy 50

4.3.4 Temperature dependence of magnetization in MnPd/Co multilayers 51

4.4 Explanation of exchange bias coupling mechanism 52

Conclusions and further direction 56

References 58