Exploring Co, Fe, and Ni Reference Layers for Single-Pulse All-Optical Reversal in Ferromagnetic Spin Valves

TL;DR

This study compares Co, Ni, and Fe reference layers in ferromagnetic spin valves to understand their role in single-pulse all-optical magnetization reversal, revealing material-dependent switching behaviors linked to ultrafast dynamics.

Contribution

It demonstrates how different reference layer materials influence all-optical magnetization reversal, highlighting the importance of ultrafast magnetization dynamics in the switching process.

Findings

Antiparallel to parallel switching occurs for all three materials.

Parallel to antiparallel switching is only observed with Co.

Rapid remagnetization of the reference layer is crucial for reversal.

Abstract

We investigate the magnetization reversal process induced by a single femtosecond laser pulse in ferromagnetic spin valves by systematically comparing reference layers composed of pure Co, Ni, and Fe. To circumvent the loss of perpendicular magnetic anisotropy associated with changes in reference layer material and thickness, we design spin valves with in plane magnetizations. While antiparallel to parallel switching is observed for all three elements, parallel to antiparallel switching occurs only with a Co reference layer and is absent with Ni and Fe. This difference is attributed to the distinct ultrafast magnetization dynamics of the reference materials. Our results support the hypothesis that parallel to antiparallel switching requires a rapid remagnetization of the reference layer, which generates a substantial negative spin current polarized opposite to the free layer magnetization an essential condition for triggering its reversal.