Title

Fabrication and optimization of magnetoresistive thin film structure for improved spintronic sensors

Alternative Title

향상된 스핀 트로닉스 센서를위한 자기 저항 박막 구조 제작 및 최적화

DGIST Authors

Kim, CheolGi ; Elzawawy, Amir Aly Ibrahim ; Lee, Hyeon-Jun

Advisor

김철기

Co-Advisor(s)

Hyeon-Jun Lee

Issued Date

2019

Awarded Date

2019-08

Citation

Amir Aly Ibrahim Elzawawy. (2019). Fabrication and optimization of magnetoresistive thin film structure for improved spintronic sensors. doi: 10.22677/thesis.200000217242

Type

Thesis

Description

Sensors

Table Of Contents

Abstract -------------------------------------------------------------------------------------------------- i
Acknowledgment -------------------------------------------------------------------------------------- iii
Table of contents ---------------------------------------------------------------------------------------- v
List of figures ------------------------------------------------------------------------------------------ viii
List of tables --------------------------------------------------------------------------------------------- x
List of abbreviations ----------------------------------------------------------------------------------- xi
Outline of the thesis ----------------------------------------------------------------------------------- xii
I. Introduction ------------------------------------------------------------------------------------------ 1
1.1 Exchange bias in FM/AFM bilayers ------------------------------------------------------------- 1
1.1.1 FM layer material and thickness effect ---------------------------------------------------- 3
1.1.2 AFM layer material and thickness effect -------------------------------------------------- 3
1.1.3 Interface roughness effect ------------------------------------------------------------------- 4
1.1.4 Seed layer effect ------------------------------------------------------------------------------ 4
1.1.5 Capping layer effect -------------------------------------------------------------------------- 5
1.2 Exchange bias in FM/NM/AFM trilayers: spacer layer material and thickness effect ---- 5
1.3 Magnetoresistance and planar Hall effect ------------------------------------------------------- 5
1.4 Planar Hall effect sensors: operating field range, output voltage, and shunt current ------ 6
1.4.1 PHE sensors without exchange bias in NiFe single layer ------------------------------- 7
1.4.2 PHE sensors with exchange bias in NiFe/IrMn bilayer --------------------------------- 9
1.4.3 PHE sensors with exchange bias in NiFe/Spacer/IrMn trilayer ------------------------ 13
1.5 Sensitivity of planar Hall effect sensors --------------------------------------------------------- 16
1.6 Noise in magnetoresistance sensors -------------------------------------------------------------- 16
1.6.1 Barkhausen noise ----------------------------------------------------------------------------- 16
1.6.2 Thermal noise --------------------------------------------------------------------------------- 17
1.6.3 1/f noise ---------------------------------------------------------------------------------------- 17
1.6.4 Reduction of noise by optimization of layer composition and sensors shape -------- 17
II. Experimental techniques ------------------------------------------------------------------------- 19
2.1 Materials --------------------------------------------------------------------------------------------- 19
2.2 Samples fabrication -------------------------------------------------------------------------------- 19
2.2.1 Photolithography method -------------------------------------------------------------------- 19
2.2.1.1 Optimization of UV exposure time and developing time ------------------------- 23
2.2.2 Lift off method -------------------------------------------------------------------------------- 24
2.2.3 DC magnetron sputtering system ----------------------------------------------------------- 24
2.2.3.1 Characterization of deposition rate --------------------------------------------------- 24
2.2.3.2 Adjustment of sample location on the sample holder with the built in magnet - 25
2.2.4 Sensor deposition ----------------------------------------------------------------------------- 28
2.2.5 Electrode deposition -------------------------------------------------------------------------- 28
2.3 Samples characterization -------------------------------------------------------------------------- 29
2.3.1 Planar Hall effect measurements ------------------------------------------------------------ 29
2.3.2 Vibrating sample magnetometry (VSM) --------------------------------------------------- 30
2.3.3 Noise measurements ------------------------------------------------------------------------- 30
2.3.4 Atomic force microscopy (AFM) ---------------------------------------------------------- 31
2.3.5 High resolution transmission electron microscopy (HR-TEM) ------------------------ 32
2.3.6 X-ray diffraction spectroscopy (XRD) ---------------------------------------------------- 32
III. Tailoring of exchange bias by material and thickness variation of seed layer ------- 33
3.1 Hybrid seed layer material and thickness effects on crystallinity and growth direction of FM and AFM layers for NiFe/IrMn bilayer---------------------------------------------------------- 33
3.2 Ta/Cu and Ta/Au hybrid seed layer effects on the exchange bias with NiFe/IrMn bilayer --------------------------------------------------------------------------------------------------------------- 39
3.3 NiFeCr seed layer effects on the exchange bias field in NiFe/Au/IrMn trilayer ----------- 40
IV. Interlayer material effects for the multilayer structures --------------------------------- 44
4.1 Effect of the NM interlayer material on the parameters of magnetic hysteresis loop for NiFe/NM/NiFe trilayers ------------------------------------------------------------------------------- 44
4.2 NiFeCr as a spacer layer in NiFe/Spacer/IrMn trilayer --------------------------------------- 48
V. Capping layer material effects on the exchange bias for multilayer structures ------- 49
5.1 NiFeCr capping layer effects on the exchange bias field in NiFe/Au/IrMn trilayer ------- 49
VI. Effect of active layers on sensor’s output voltage, operating field range, sensitivity and noise in multilayer structures ----------------------------------------------------------------- 51
6.1 NiFeCr as an active FM layer and AFM in comparison with NiFe/IrMn bilayer structure --------------------------------------------------------------------------------------------------------------- 51
6.2 Magnetic field sensitivity of PHE sensors, based on NiFe/Au/IrMn trilayer junctions, grown with Ta and NiFeCr seed and capping layers -------------------------------------------------------- 52
6.3 Optimization of sensitivity by material and thickness variation of FM layer in FM/IrMn bilayer ---------------------------------------------------------------------------------------------------- 57
6.4 Untethered operating field range adjustment by interdependent variation of non-magnetic spacer and capping layers thicknesses ---------------------------------------------------------------- 67
6.5 Magnetoresistance response in sweeping magnetic field for NiFe/NM/NiFe trilayer ----- 73
6.6 Uncorrelated responses of PHE and AMR to Barkhausen jumps in sweeping magnetic field for NiFe/NM/NiFe trialyer ----------------------------------------------------------------------------- 77
6.7 The planar Hall voltage noise in stationery magnetic field for NiFe/NM/NiFe trialyer --- 82
Conclusions and perspectives ----------------------------------------------------------------------- 87
List of publications ------------------------------------------------------------------------------------ 93
List of conferences ------------------------------------------------------------------------------------- 94
Summer school and internship ---------------------------------------------------------------------- 97
References ---------------------------------------------------------------------------------------------- 98

URI

http://dgist.dcollection.net/common/orgView/200000217242
http://hdl.handle.net/20.500.11750/10459

DOI

10.22677/thesis.200000217242

Degree

Doctor

Department

Department of Emerging Materials Science

Publisher

DGIST

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