Scaling Projections on Spin Transfer Torque Magnetic Tunnel Junctions

TL;DR

This paper analyzes how scaling magnetic tunnel junction devices affects their electrical and magnetic properties, revealing size-dependent behaviors in resistance, magnetoresistance, and switching energy using non-equilibrium Green's function formalism.

Contribution

It provides a detailed study of the impact of device scaling on MTJs with different configurations and geometries, highlighting the role of transverse mode energy profiles.

Findings

Ultra-high magnetoresistance at small cross-sectional areas.

Constant tunnel magnetoresistance at larger areas.

Oscillatory behavior in pentalayer devices at small areas.

Abstract

We investigate scaling of technologically relevant magnetic tunnel junction devices in the trilayer and pentalayer configurations by varying the cross-sectional area along the transverse direction using the non-equilibrium Green's function spin transport formalism. We study the geometry dependence by considering square and circular cross-sections. As the transverse dimension in each case reduces, we demonstrate that the transverse mode energy profile plays a major role in the resistance-area product. Both types of devices show constant tunnel magnetoresistance at larger cross-sectional areas but achieve ultra-high magnetoresistance at small cross-sectional areas, while maintaining low resistance-area products. We notice that although the critical switching voltage for switching the magnetization of the free layer nanomagnet in the trilayer case remains constant at larger areas, it needs more energy to switch at smaller areas. In the pentalayer case, we observe an oscillatory behavior at smaller areas as a result of double barrier tunneling. We also describe how switching characteristics of both kinds of devices are affected by the scaling.