Microscopic origin of hard-plane antiferromagnetism in the Kondo lattice Ce2Rh3Ge5

TL;DR

This paper uncovers the microscopic mechanism behind the rare hard-plane antiferromagnetic order in Ce$_2$Rh$_3$Ge$_5$, showing how partial 4f-moment delocalization and RKKY exchange invert single-ion anisotropy.

Contribution

It introduces a unified microscopic framework explaining how partial 4f delocalization and RKKY exchange lead to hard-plane antiferromagnetism in a strongly hybridized Kondo lattice.

Findings

Neutron diffraction shows moments in the $ab$ plane.

Inelastic neutron scattering indicates a $c$-axis easy magnetization in the paramagnetic state.

The study establishes competition between single-ion anisotropy, Kondo screening, and RKKY exchange.

Abstract

Hard plane antiferromagnetic order where ordered moments lie perpendicular to the single-ion crystal electric field easy axis is rare in Ce-based Kondo lattices and is a subject of active interest. Here we show that Ce$_2$Rh$_3$Ge$_5$ realizes a hard-plane antiferromagnetic state in which partial delocalization of the local moment gives rise to an RKKY exchange that overturns the single-ion easy-axis preference. Neutron diffraction reveals moments in the $ab$ plane, while inelastic neutron scattering and susceptibility establish a magnetic easy axis along $c$ in the paramagnetic regime, highlighting a clear inversion between single-ion and ordered-state anisotropies. In this work, we establish a unified microscopic framework to consistently account for partial $4f$-moment delocalization, enhanced in-plane RKKY exchange, and the resulting hard-plane antiferromagnetic order. Ce$_2$Rh$_3$Ge$_5$ thus provides a benchmark system in which single-ion anisotropy, Kondo screening, and RKKY exchange compete on comparable energy scales, revealing a cooperative route to hard-axis ordering in strongly hybridized Kondo lattices.