Eur. Phys. J. B 59, 463-469 (2007)
https://doi.org/10.1140/epjb/e2007-00083-9

Hard axis magnetic field dependence on current-induced magnetization switching in MgO-based magnetic tunnel junctions

¹ Corporate R & D Center, Toshiba Corporation, 212-8582 Kawasaki, Japan and CREST, Japan Science and Technology Agency (JST), Kawaguchi, 332-0012, Saitama, Japan
² National Institute for Materials Science, 1-2-1, Sengen, 305-0047 Tsukuba, Japan and CREST, Japan Science and Technology Agency (JST), Kawaguchi, 332-0012, Saitama, Japan

Corresponding author: ^a yoshiaki.saito@toshiba.co.jp

Received: 28 September 2006
Revised: 15 February 2007
Published online: 28 March 2007

Abstract

We conducted a detailed study of hard axis magnetic field (H_hard) dependence on current-induced magnetization switching (CIMS) in MgO-based magnetic tunnel junctions (MTJs) with various junction sizes and various uniaxial anisotropy fields. The decreases in critical current density (J_c) and the intrinsic critical current density (J_c0) estimated from the pulse duration dependence on J_c in CIMS are observed when applying H_hard for all MTJs. The decrease in energy barrier of CIMS is also observed except for the largest sample. These results indicate that the reduction of J_c is attributable to both the increase of spin-transfer efficiency and the decrease in energy barrier in the case of applying H_hard. The J_c0 decreases with increase in the mutual angle between the direction of magnetization and the easy axis (θ_f), which is consistent with the theoretical prediction proposed by Slonczewski. The degree of the reduction of J_c0 for the same value of H_hard decreases with decreasing size of MTJs. This behavior is considered to be related to not only decrease in θ_f due to the increase in anisotropy field in MTJs, but also to the increase in the variance of the initial angle of magnetization due to the thermally activated magnon excitation. The stable switching endurance related to CIMS was observed in a wide range of MTJ sizes when applying H_hard. Moreover, we proposed a new architecture and a new switching method considering write disturbance. These results would be useful for application to spin memory and other spin-electronic devices.