Physical Review B

Stochastic magnetic tunnel junction with easy-plane dominant anisotropy

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We experimentally explore an easy-plane dominant magnetic tunnel junction's thermal stochastic fluctuation for possible applications in physical random number generation for computing. We use materials and fabrication methods similar to those in spin-transfer-torque based magnetic random access memory technology. This work provides an experiment-based view of the device properties that could be optimized for use as an entropy source. We illustrate some relevant device-level metrologies and show several materials and device-physics related factors one could further investigate. Those include the role of a combined strong easy-plane and a weak in-plane anisotropy on fluctuation, the combined stochastic dynamics of the free and reference layer of such magnetic tunnel junctions under bias-voltage induced spin-current drive, and the dynamics' dependence on bias voltage, on magnetic field, and on device and materials parameters in need of control. These observations provide a base-line view of such stochastic tunnel junctions for future applications-specific optimization.