11:30 〜 11:45
▲ [19a-D104-10] Antiferromagnetic layer thickness dependence of mangnetoelectric switching condition of perpendicular exchange bias
キーワード：perpendicular exchange bias, magnetoelectric switching of exchange bias, Antiferromagnetic based spintronics
Perpendicular exchange bias (PEB), appeared at the antiferromagnetic (AFM)/ferromagnetic interface, is of vital importance to realize modern spintronic devices. Using a magnetoelectric (ME) AFM Cr2O3 enabled the electric field control of PEB [1,2]. In the previous research, we have reversibly, isothermally switched the PEB in typical Cr2O3/Co stack films. We found the relationship between the applied magnetic field and threshold electric field for the ME switching of PEB (EH curve) with a contribution of AFM moments to the total free energy of the system [3]. In this study, to get a deeper understanding of the ME switching, we further investigated the dependence of the energy condition on the thickness of the AFM layer (tAFM).
The stacked films Pt(1.2 nm)/Co(0.4 nm)/Au(0.5 nm)/Cr2O3(tAFM = 115 nm, 130 nm, 147 nm, 169nm, 170 nm, 212 nm)/Pt(20 nm) were fabricated by using DC magnetron sputtering. Using a reversible isothermal electric tuning approach, the ME switching was investigated by the anomalous Hall effect measurements at the similar reduced temperature T/TN = 0.987 in order to exclude the thermal effect in the ME switching process (TN is the Néel temperature determined from the temperature dependence of the PEB field). Based on the previously proposed energy condition, i.e. a(E-E0)H = ± 2KAFM - JINT/tAFM (where a is a ME coefficient of Cr2O3) [3], we estimated the tAFM dependence of the magnetic anisotropy energy (KAFM), the interface exchange coupling (JINT), and the critical electric field (E0). KAFM decreases as tAFM increases, which suggests a magnetic domain wall process (Fig. 1a). The asymmetry of the switching condition is also quantitated by JINT. JINT and the unidirectional magnetic anisotropy energy JK (=HEB×MS×tFM) are correlated well, suggesting that the asymmetry is caused by the unidirectional nature of the interfacial exchange coupling. The critical electric field E0 decreases with the increase of Cr2O3 thickness, which indicated that the E0 is originated from the interface uncompensated AFM moments.
The stacked films Pt(1.2 nm)/Co(0.4 nm)/Au(0.5 nm)/Cr2O3(tAFM = 115 nm, 130 nm, 147 nm, 169nm, 170 nm, 212 nm)/Pt(20 nm) were fabricated by using DC magnetron sputtering. Using a reversible isothermal electric tuning approach, the ME switching was investigated by the anomalous Hall effect measurements at the similar reduced temperature T/TN = 0.987 in order to exclude the thermal effect in the ME switching process (TN is the Néel temperature determined from the temperature dependence of the PEB field). Based on the previously proposed energy condition, i.e. a(E-E0)H = ± 2KAFM - JINT/tAFM (where a is a ME coefficient of Cr2O3) [3], we estimated the tAFM dependence of the magnetic anisotropy energy (KAFM), the interface exchange coupling (JINT), and the critical electric field (E0). KAFM decreases as tAFM increases, which suggests a magnetic domain wall process (Fig. 1a). The asymmetry of the switching condition is also quantitated by JINT. JINT and the unidirectional magnetic anisotropy energy JK (=HEB×MS×tFM) are correlated well, suggesting that the asymmetry is caused by the unidirectional nature of the interfacial exchange coupling. The critical electric field E0 decreases with the increase of Cr2O3 thickness, which indicated that the E0 is originated from the interface uncompensated AFM moments.