Giant coercivity, resistivity upturn, and anomalous Hall effect in ferrimagnetic FeTb

TL;DR

This study investigates the magnetic and transport properties of amorphous FeTb ferrimagnetic alloys, revealing giant coercivity, resistivity upturn, and anomalous Hall effect behavior, advancing understanding of transition-metal-rare-earth ferrimagnets.

Contribution

It provides a systematic analysis of FeTb alloys' coercivity and transport properties, highlighting the impact of layer thickness and temperature without changing composition.

Findings

Coercivity follows $1/ ext{cos} heta_H$ scaling and increases exponentially with cooling.

Resistivity shows a quasi-linear upturn upon cooling, likely due to thermal vibrations.

Anomalous Hall effect scaling laws break down in amorphous FeTb alloys.

Abstract

Despite the blooming interest, the transition-metal rare-earth ferrimagnets have not been comprehensively understood in terms of their coercivity and transport properties. Here, we report a systematic study of the magnetic and transport properties of ferrimagnetic FeTb alloy by varying the layer thickness and temperature. The FeTb is tuned from the Tb-dominated regime to the Fe-dominated regime via the layer thickness, without varying the composition. The coercivity closely follows the $1/\cos\theta_H$ scaling (where $\theta_H$ is the polar angle of the external magnetic field) and increases quasi-exponentially upon cooling (exceeding 90 kOe at low temperatures), revealing that the nature of the coercivity is the thermally-assisted domain wall depinning field. The resistivity exhibits a quasi-linear upturn upon cooling possibly due to thermal vibrations of the structure factor of the amorphous alloy. The existing scaling laws of the anomalous Hall effect in the literature break down for the amorphous FeTb that are either Fe- or Tb-dominated. These findings should advance the understanding of the transition-metal-rare-earth ferrimagnets and the associated ferrimagnetic phenomena in spintronics.