# H-T Phase Diagram of Rare-Earth -- Transition Metal Alloy in the Vicinity of the Compensation Point

## TL;DR

This paper constructs an H-T phase diagram for GdFeCo ferrimagnetic alloy, explaining anomalous hysteresis loops near the compensation point through a two-sublattice model considering magnetic anisotropy.

## Contribution

It introduces a two-sublattice model with anisotropy considerations to explain high-field magnetic behavior near the compensation point.

## Key findings

- Tricritical point can be at higher temperature than the compensation point.
- Hysteresis loop shape is strongly temperature dependent near the compensation point.
- High-field magnetic phase transition explains anomalous hysteresis loops.

## Abstract

Anomalous hysteresis loops of ferrimagnetic amorphous alloys in high magnetic field and in the vicinity of the compensation temperature have so far been explained by sample inhomogeneities. We obtain H-T magnetic phase diagram for ferrimagnetic GdFeCo alloy using a two-sublattice model in the paramagnetic rare-earth ion approximation and taking into account rare-earth (Gd) magnetic anisotropy. It is shown that if the magnetic anisotropy of the $f$-sublattice is larger than that of the $d$-sublattice, the tricritical point can be at higher temperature than the compensation point. The obtained phase diagram explains the observed anomalous hysteresis loops as a result of high-field magnetic phase transition, the order of which changes with temperature. It also implies that in the vicinity of the magnetic compensation point the shape of magnetic hysteresis loop is strongly temperature dependent.