Analysis of the Electrical Characteristics for Compact SPICE Modelling of STT-MTJ Device with Physical Parameters Variation

Spin-Transfer Torque Magnetoresistive Random Access Memory (STT-MRAM) operates on the principle of magnetic anisotropy energy to retain information and magnetoresistance to retrieve information. STT-MRAM consists of an MTJ (Magnetic Tunnel Junction) and a transistor device. The MTJ comprises two layers of ferromagnetic metal separated by an insulator. A major concern in evaluating STT-MRAM technology is developing a scalable MTJ compact model capable of incorporating real variable effects across numerous technical nodes. Therefore, this work involves simulating the STT-MTJ device compact SPICE modeling at the device level using a SPICE subcircuit and a mathematical model to analyze the electrical characteristics. The I-V characteristics of parallel and anti-parallel orientations of the STT-MTJ are simulated. The parallel resistance (RP) and anti-parallel resistance (RAP) of the STT-MTJ device are varied from their original values to observe the I-V characteristic graph for each case. The I-V characteristics for different resistance values and variations in width and length are analyzed. It is observed that the Tunneling Magnetoresistance (TMR) increases by 230.77% when the resistance for parallel current (IP) is reduced, whereas the TMR increases by 105.56% when the resistance for anti-parallel current (IAP) is reduced. Moreover, as the width and length of the Free Layer (FL) increase (by 222.22%), the write current for the MTJ also increases by 492.55%. The parameters used in the STT-MTJ can be adjusted for different MTJ materials to achieve higher performance efficiency.