True physics based, scalable for future nodes, user-friendly, and fully-compatible with SPICE simulator.

An MTJ SPICE model allows circuit designers to simulate key aspects of spin-transfer torque MRAM (STT-MRAM) such as read and write delays. Our self-contained, physics-based magnetic tunnel junction (MTJ) SPICE model can reproduce realistic MTJ characteristics based on user-defined input parameters such as the free layer's length, width, and thickness parameters. Using the MTJ SPICE Model, scalability studies of both in-plane and perpendicular MTJs can be performed across different technology nodes with minimal effort.


J. Kim, A. Chen, B. Behin-Aein, S. Kumar, J.P. Wang, and C.H. Kim, "A Technology-Agnostic MTJ SPICE Model with User-Defined Dimensions for STT-MRAM Scalability Studies", Custom Integrated Circuits Conference (CICC), Sep. 2015. Download the slides.

Getting started

  1. Download MTJ spice model.
  2. Extract .zip file.
  3. Open MTJ_write.sp file (MTJ write example)
  4. Set MTJ dimensions and material parameters: Ms0, P0, alpha, RA and initial temperature
    • Ms0: saturation magnetization, P0: polarization, both at zero Kelvin temperature
  5. Select anisotropy type using parameter 'MA'
    • In-plane magnetic anisotropy: MA='0' and Perpendicular magnetic anisotropy: MA='1'
  6. Select the initial state of free layer using parameter 'ini', and apply voltage with correct polarity. Magnetization of the fixed layer will be set automatically according to the 'ini' value
    • Antiparallel to parallel switching : ini='1' with positive voltage
    • Parallel to antiparallel switching: ini='0' with negative voltage
  7. Run SPICE simulation