The Azimuthal Dependence of Exchange Bias Effect and its Analysis by Spin Glass Model in Ni0.8Fe0.2/CoxNi1−xO Bilayers

Woosuk Yoo,Myung-Hwa Jung,Kyujoon Lee,Chun-Yeol You,Jung-Il Hong,Sinyong Jo,Seongmin Choo

doi:10.1109/access.2021.3055521

Abstract

Exchange bias (EB) effect has been vigorously researched for many years due to its possible applications in information storage and spintronics, especially in spin valves for magnetic recording devices. Even though many models have been expounded to this day, they do not prove convincingly the origins of EB effect. We attempt to establish the azimuthal dependence of EB effect with respect to varying the composition of the antiferromagnet Co x Ni 1-x O and temperature. In this report, we deposited the bilayer thin films of Ni 0.8 Fe 0.2 /Co x Ni 1-x O with x varying from 0.4 to 0.8 by magnetron sputtering and studied the variation of exchange bias field and coercivity. The EB effect was investigated for various external parameters such as temperature, the composition of antiferromagnetic layer, and the direction of magnetic field. The comparison between the calculations and experimental data showed good consistency with the spin glass model, and we suggest the validity of spin glass model to understand the origin of exchange bias effect in the Ni 0.8 Fe 0.2 /Co x Ni 1-x O bilayers.

Highlights

Since exchange bias (EB) effect was discovered by Meiklejohn and Bean in 1956 [1], [2], great interest has been shown to the phenomena due to it’s possible applications in information storage and spintronics, especially in spin valves for magnetic recording devices
We have summarized the parameters γ and f obtained from the azimuthal dependence of HEB and the anisotropic magnetoresistance (AMR) fitting of all the samples measured at 300 K by the spin glass model
The HEB and HC were calculated based on two different models, the Mauri model, and the spin glass model, to explain the measured results

Summary

INTRODUCTION

Since exchange bias (EB) effect was discovered by Meiklejohn and Bean in 1956 [1], [2], great interest has been shown to the phenomena due to it’s possible applications in information storage and spintronics, especially in spin valves for magnetic recording devices. The magnitude of shift of hysteresis loop is called as EB field (HEB) This EB effect has been widely used in magnetic devices especially pinning the fixed layer in read heads of hard disk drives. In this study we use the alloyed system of CoO and NiO to tune the antiferromagnetic anisotropy (KAFM) and the Néel temperature to achieve large exchange bias which work at room temperature. The results show that our measurements show qualitative agreement with the spin glass model To verify this agreement with the spin glass, we measured the temperature dependence of HEB from extremely low temperature (5 K) to TB and the training effect at 5 K

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSION