# Structural and magnetic properties of GdCo$_{5-x}$Ni$_x$

## TL;DR

This study investigates how substituting nickel into GdCo$_5$ affects its structural and magnetic properties, revealing changes in compensation temperature, coercivity, and magnetocrystalline anisotropy through experiments and theoretical calculations.

## Contribution

It provides new insights into the effects of Ni substitution on GdCo$_5$'s magnetic behavior, combining experimental synthesis, characterization, and density-functional theory analysis.

## Key findings

- Compensation temperature increases with Ni content for 1 ≤ x ≤ 3.
- Peak coercivity observed at x ≈ 1 at 10K.
- Density-functional theory reproduces magnetization and anisotropy trends.

## Abstract

GdCo$_5$ may be considered as two sublattices - one of Gd and one of Co - whose magnetizations are in antiparallel alignment, forming a ferrimagnet. Substitution of nickel in the cobalt sublattice of GdCo$_5$ has been investigated to gain insight into how the magnetic properties of this prototype rare-earth/transition-metal magnet are affected by changes in the transition metal sublattice. Polycrystalline samples of GdCo$_{5-x}$Ni$_x$ for 0 $ \leq x \leq $ 5 were synthesized by arc melting. Structural characterization was carried out by powder x-ray diffraction and optical and scanning electron microscope imaging of metallographic slides, the latter revealing a low concentration of Gd$_2$(Co, Ni)$_7$ lamellae for $x \leq 2.5$. Compensation - i.e. the cancellation of the opposing Gd and transition metal moments is observed for $1 \leq x \leq 3$ at a temperature which increases with Ni content; for larger $x$, no compensation is observed below 360 K. A peak in the coercivity is seen at $x \approx 1$ at 10K coinciding with a minimum in the saturation magnetization. Density-functional theory calculations within the disordered local moment picture reproduce the dependence of the magnetization on Ni content and temperature. The calculations also show a peak in the magnetocrystalline anisotropy at similar Ni concentrations to the experimentally observed coercivity maximum.