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

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 an FM
₁
-I
₃
-FM
₄
structure, where FM
₁
and FM
₄
are ferromagnetic electrodes and I3 is 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 the FM
₁
-I
₃
-FM
₄
MTJ, 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 layer (M
₂
) between one of the ferromagnetic electrodes, FM
₁
or FM
₄
, and the insulator I
₃
. The M
₂
-inserted MTJ is the FM
₁
-M
₂
-I
₃
-FM
₄
structure. The inserted M
₂
layer leads to a severe alteration of the M
₂
-I
₃
interface, 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-A1
₂
O
₃
-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 the M
₂
-I
₃
interface. The proposed method uses a gate voltage on the M
₂
layer to alter the potential profile at the M
₂
-I
₃
interface, and to modulate the TMR ratio in the FM
₁
-M
₂
-I
₃
-FM
₄
MTJ.