The Behavior Analysis of Magnetoresistive Tunnel Junction Devices in State Space

The behavior of magnetoresistive tunnel junction (MTJ) devices in the electronic (digital) circuits is governed by several differential equations. The LLG equation determines the dynamic of the magnetic polarization vector which ultimately affects the (anti)parallel resistance of MTJs. This vector differential equation is decomposed into two scalar differential equations. In the proposed method, the differential equations are expressed in the state space and the corresponding well-developed theories are applied. In fact, the device is considered as a multi-input multi-output control system and the qualitative solutions are presented. The state diagram gives an insight into the device behavior. It can provide additional information about the device performance and can be considered as a complementary technique of other available analysis approaches. With this ability, the designer can engineer the MTJ devices for their optimum performance in the circuit. Using this theory, we also suggested a power and performance improving approach for the spin transfer torque MTJ-based logic circuits. To show the efficiencies offered by the proposed method, a STT-MRAM cell and an array are designed and it is shown that better specifications can be achieved in terms of switching time and power dissipation. The reliability issues are also investigated and we show that the proposed power/performance improvement approach can effectively consider the reliability concerns.