Unusual strong ferromagnetism in site-ordered cubic Laves phase compound LuInCo$_4$ with Co-pyrochlore lattice

TL;DR

This paper reports the synthesis and characterization of a new cubic Laves phase compound, LuInCo$_4$, which exhibits strong ferromagnetism at 306 K, driven by Co-3d flat bands, with unique anisotropic magnetic properties and a metamagnetic transition.

Contribution

First synthesis of LuInCo$_4$ with a Co-pyrochlore lattice, revealing unusual strong ferromagnetism and anisotropic magnetic behavior in a pyrochlore metal.

Findings

LuInCo$_4$ undergoes ferromagnetic transition at 306 K

Saturation magnetization of 3.43 μ_B/f.u. at 5 K

Displays anisotropic magnetization and a metamagnetic transition

Abstract

We have successfully synthesized single crystals of the site-ordered cubic (C15b) Laves phase compound LuInCo$_4$ with the Co-pyrochlore sublattice for the first time. LuInCo$_4$ undergoes a ferromagnetic transition at 306 K and has a saturation moment of 3.43 $\mu_{\rm{B}}$/f.u. at 5 K. The strongly ferromagnetic nature was verified by DFT calculations, suggesting that Co-3$d$ flat bands near the Fermi level induce the spin polarization. The magnetization is isotropic above $\sim$100 K, saturates most easily in the [100] direction at low temperatures. In this anisotropic ferromagnetic state, the magnetization undergoes a metamagnetic transition in the [111] direction. Our results suggest that LuInCo$_4$ is a new strong but unusual itinerant electron ferromagnet, which deserves further study as a pyrochlore metal.