Gate-voltage Controlled Tunneling Magnetoresistance in a Magnetic Tunneling Junction with an Inserted Thin Metallic Layer

摘要

Magnetic tunneling junctions (MTJs) continue to receive considerable attention because of their large tunneling magnetoresistance (TMR) effect not only for the depth of fundamental phenomena available, but also for the potential and proven applications [1]–[4]. An MTJ consists of ann$FM_{1}-I_{3}-FM_{4}$nstructure, wheren$FM_{1}$nandn$FM_{4}$nare ferromagnetic electrodes andn$I_{3}$nis a thin insulator. The TMR effect originates from spin-dependent tunneling (SDT) in a MTJ. The change of SDT in the MTJ is measured by the TMR ratio. In then$FM_{1}-I_{3}-FM_{4}$nMTJ, SDT is extremely sensitive to the interface structures between the insulator and each electrode. Thus, modulating one of the interfaces can change the TMR. One way to achieve this is to insert a thin nonmagnetic metallic layern$(M_{2})$nbetween one of the ferromagnetic electrodes,n$FM_{1}$norn$FM_{4}$n, and the insulatorn$I_{3}$n. Then$M_{2}$n-inserted MTJ is then$FM_{1}-M_{2}-I_{3}-FM_{4}$nstructure. The insertedn$M_{2}$nlayer leads to a severe alteration of then$M_{2}-I_{3}$ninterface, thus resulting in a dramatic effect on SDT and the TMR ratio. The excellent experimental work of Yuasa et al. shows how the TMR is affected by the inserted Cu metal in a high-quality Co-Cu-A1n2nOn3n-NiFe MTJ [1]. A distinct attenuated oscillation of the TMR ratios with increasing the Cu thickness is observed at room temperature when the inserted Cu thickness is less than to 29Å. Here, we propose a method of changing then$M_{2}-I_{3}$ninterface. The proposed method uses a gate voltage on then$M_{2}$nlayer to alter the potential profile at then$text{M}_{2}-text{I}_{3}$ninterface, and to modulate the TMR ratio in then$FM_{1}-M_{2}-I_{3}-FM_{4}$nMTJ.