# Sub-nanosecond switching in a cryogenic spin-torque spin-valve memory element with a dilute permalloy free layer

## TL;DR

This study demonstrates that using a dilute permalloy free layer in cryogenic spin-torque spin-valve memory significantly reduces switching time and energy, advancing low-power magnetic memory technology.

## Contribution

It introduces a novel application of dilute permalloy free layers to achieve sub-nanosecond switching speeds in cryogenic spin-valve devices.

## Key findings

- Dilute permalloy free layer switches in 0.475 ns
- Reduced spin torque asymmetry and polarization observed
- Lower switching energy achieved with dilute permalloy

## Abstract

We present a study of the pulsed current switching characteristics of spin-valve nanopillars with in-plane magnetized dilute permalloy and undiluted permalloy free layers in the ballistic regime at low temperature. The dilute permalloy free layer device switches much faster: the characteristic switching time for a permalloy free (Ni0.83Fe0.17) layer device is 1.18 ns, while that for a dilute permalloy ([Ni0.83Fe0.17]0.6Cu0.4) free layer device is 0.475 ns. A ballistic macrospin model can capture the data trends with a reduced spin torque asymmetry parameter, reduced spin polarization and increased Gilbert damping for the dilute permalloy free layer relative to the permalloy devices. Our study demonstrates that reducing the magnetization of the free layer increases the switching speed while greatly reducing the switching energy and shows a promising route toward even lower power magnetic memory devices compatible with superconducting electronics.