Electronic and magnetic properties of $\alpha$-FeGe$_2$ films embedded in vertical spin valve devices

TL;DR

This study explores the electronic and magnetic properties of $ extalpha$-FeGe$_2$ films embedded in spin valve devices, revealing temperature-dependent magnetic transitions and spin transport behaviors consistent with first-principles calculations.

Contribution

It demonstrates the integration of a novel layered tetragonal $ extalpha$-FeGe$_2$ as a spacer in spin valves and characterizes its magnetic and transport properties.

Findings

Spin valve operation achieved with $ extalpha$-FeGe$_2$ spacers.

Spin valve signals increase with temperature and spacer thickness.

Ferromagnetic phase transition observed between 55 and 110 K.

Abstract

We studied metastable $\alpha$-FeGe$_2$, a novel layered tetragonal material, embedded as a spacer layer in spin valve structures with ferromagnetic Fe$_3$Si and Co$_2$FeSi electrodes. For both types of electrodes, spin valve operation is demonstrated with a metallic transport behavior of the $\alpha$-FeGe$_2$ spacer layer. The spin valve signals are found to increase both with temperature and spacer thickness, which is discussed in terms of a decreasing magnetic coupling strength between the ferromagnetic bottom and top electrodes. The temperature-dependent resistances of the spin valve structures exhibit characteristic features, which are explained by ferromagnetic phase transitions between 55 and 110~K. The metallic transport characteristics as well as the low-temperature ferromagnetism are found to be consistent with the results of first-principles calculations.