Highly anisotropic geometrical Hall effect via f-d exchange fields in doped pyrochlore molybdates

TL;DR

This study reveals a highly anisotropic geometrical Hall effect in doped pyrochlore molybdates driven by non-coplanar exchange fields from localized magnetic moments, even without long-range magnetic order of conduction electrons.

Contribution

It demonstrates the emergence of the geometrical Hall effect in doped pyrochlore molybdates due to non-coplanar exchange fields, independent of conduction electron magnetic order.

Findings

The geometrical Hall effect is observed without long-range magnetic order.

The effect is highly anisotropic with respect to magnetic field direction.

The Hall effect correlates with the scalar spin chirality of local Tb moments.

Abstract

When a conduction electron couples with a non-coplanar localized magnetic moment, the realspace Berry curvature is exerted to cause the geometrical Hall effect, which is not simply proportional to the magnetization. So far, it has been identified in the case mostly where the non-coplanar magnetic order is present on the sublattice of conduction electrons. Here, we demonstrate that the geometrical Hall effect shows up even without long-range magnetic order of conduction electrons, as induced by non-coplanar exchange fields from the localized magnetic moments, in hole-doped phyrochlore molybdates. We find that the geometrical Hall effect is markedly anisotropic with respect to the applied magnetic field direction, which is in good accordance with the field-dependent magnitude and sign change of the real-space scalar spin chirality of local Tb moments. These results may facilitate the understanding of emergent electromagnetic responses induced by the Kondo-like coupling between conduction electrons and local spins in a broad material class.