Frustration and relaxation of antiferromagnetic domains reversed by magneto-electric field cooling in a Pt/Co/Au/Cr2O3/Pt-stacked film

Yu Shiratsuchi,Shogo Yonemura,Ryoichi Nakatani,Tatsuo Shibata,Shunsuke Watanabe

doi:10.1063/1.5053136

Abstract

Using magnetic domain observations, we investigated the reversal process of the perpendicular exchange bias polarity resulting from the antiferromagnetic Cr2O3 domain reversal driven by magneto-electric field cooling (MEFC). The exchange bias polarity changed from negative to positive with increasing electric field during MEFC. The relevant change in the magnetic domain revealed the stochastic appearance of the reversed magnetic domains that exhibit the positive exchange bias. The local magnetization curves suggest that the antiferromagnetic domain state after MEFC was frustrated because of energy competition between the interfacial exchange coupling and the bulk magneto-electric effect. The frustrated nature of the magnetic domain structure is supported by the training effect of the exchange bias after MEFC.

Highlights

Antiferromagnetic (AFM) spintronics has attracted increasing interest because of its potential for use in applications such as ultra-high-density storage and for investigations in fundamental physics such as ultrafast spin dynamics in the terahertz regime.[1,2] A key technique of AFM spintronics is controlling AFM spins and/or AFM domains
Domain is common for the ME-induced switching. In these two cases, the Cr2O3 thickness is highly different: typically 0.5 mm for the former case and 150 nm for our case, implying that the frustration of the AFM domain state occurred in the vicinity of the interface, consistent with the above supposed mechanism to generate the frustration of the AFM domain state. To verify that this frustrated AFM domain state was the result of MEFC, i.e., the above-mentioned energy competition, we further investigated the magnetization curves and the training effect after conventional zero-field cooling (ZFC)
We have investigated the change in the magnetic domain pattern accompanying switching of the perpendicular exchange bias driven by MEFC

Summary

INTRODUCTION

Antiferromagnetic (AFM) spintronics has attracted increasing interest because of its potential for use in applications such as ultra-high-density storage and for investigations in fundamental physics such as ultrafast spin dynamics in the terahertz regime.[1,2] A key technique of AFM spintronics is controlling AFM spins and/or AFM domains. On the basis of this finding, in this study we have investigated the change in the magnetic domain pattern induced by ME-induced switching of the perpendicular exchange bias through the FM domain observation using a magneto-optic Kerr effect (MOKE) microscope. The MEFC technique was employed to switch the perpendicular exchange bias polarity.[8,10,11,17,18] In principle, MEFC should be started from above the Neel temperature of the Cr2O3 layer. For the FM/AFM stacked film, the Neel temperature can be estimated based on the temperature dependence of the exchange bias field HEX.[24] HEX vanished at FIG. Using the fabricated micro-dot, magnetic domain observations by means of the MOKE microscope were carried out. The microscope was designed so that the magnetic domain with perpendicular magnetization was observable

RESULTS AND DISCUSSION

H EX max and

SUMMARY