Giant Hall effect in a highly conductive frustrated magnet GdCu$_2$

TL;DR

This study reports an exceptionally large Hall effect in the highly conductive frustrated magnet GdCu$_2$, revealing complex interactions between magnetization, electronic structure, and spin fluctuations.

Contribution

It uncovers the giant Hall effect in GdCu$_2$ and explains its origin through spin-splitting, Fermi pocket dynamics, and skew scattering mechanisms.

Findings

Hall conductivity reaches 4 x 10^4 Ω^{-1}cm^{-1} at low temperature

Sign changes in Hall conductivity under magnetic fields

Giant Hall effect suppressed by temperature and disorder

Abstract

The Hall effect is one of the most fundamental but elusive phenomena in condensed matter physics due to the rich variety of underlying mechanisms. Here we report an exceptionally large Hall effect in a frustrated magnet GdCu$_2$ with high conductivity. The Hall conductivity at the base temperature is as high as 4 x 10$^4$ $\Omega^{-1}$cm$^{-1}$ and shows abrupt sign changes under magnetic fields. Remarkably, the giant Hall effect is rapidly suppressed as the longitudinal conductivity is lowered upon increasing temperature or introducing tiny amount of quenched disorder. Our systematic transport measurements together with neutron scattering measurements and ab initio band calculations indicate that the unusual Hall effect can be understood in terms of spin-splitting induced emergence/disappearance of Fermi pockets as well as skew scattering from spin-chiral cluster fluctuations in a field-polarized state. The present study demonstrates complex interplay among magnetization, spin-dependent electronic structure, and spin fluctuations in producing the giant Hall effect in highly conductive frustrated magnets.