Tunable tunneling magnetoresistance in a ferromagnet-metal-insulator-ferromagnet tunneling junction

The tunneling magnetoresistance (TMR) ratio is investigated in a ferromagnet-metal-insulator-ferromagnet planar tunneling junction by use of the spin-polarized free-electron model. In this paper, the bias voltage is exploited to alter the tunneling direction and to tune the barrier height of the insulator, and then to shift oscillatory peaks of the attenuated TMR ratio. We find that the phase change between the forward and backward bias voltages is larger than the phase change due the strength of the bias voltages, and that the direction of the bias voltages can be used to control the sign of the TMR ratio if the wave vector within the M-2 layer is close to the imaginary wave vector within the I-3 insulator. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3357331]