Magnetic structures in the rich magnetic phase diagram of Ho$_2$RhIn$_8$

TL;DR

This study elucidates the complex magnetic structures of Ho$_2$RhIn$_8$ across its phase diagram, revealing detailed propagation vectors and magnetic order in multiple phases through neutron diffraction experiments.

Contribution

First detailed neutron diffraction analysis of all magnetic phases in Ho$_2$RhIn$_8$, including incommensurate and field-induced phases, with results aligning with crystal field theory predictions.

Findings

Identification of magnetic propagation vectors in all phases.

Magnetic moments align along the tetragonal c axis.

Incommensurate AF3 phase characterized by specific propagation vector.

Abstract

The magnetic phase diagram of the tetragonal Ho$_2$RhIn$_8$ compound has similar features to many related systems, revealing a zero magnetic field AF1 and a field-induced AF2 phases. Details of the magnetic order in the AF2 phase were not reported yet for any of the related compounds. In addition, only the Ho$_2$RhIn$_8$ phase diagram contains a small region of the incommensurate zero-field AF3 phase. We have performed a number of neutron diffraction experiments on single crystals of Ho$_2$RhIn$_8$ using several diffractometers including experiments in both horizontal and vertical magnetic fields up to 4 T. We present details of the magnetic structures in all magnetic phases of the rich phase diagram of Ho$_2$RhIn$_8$. The Ho magnetic moments point along the tetragonal $c$ axis in every phase. The ground-state AF1 phase is characterized by propagation vector $\textbf{k}$ = (1/2, 0, 0). The more complex ferrimagnetic AF2 phase is described by four propagation vectors $\textbf{k}_{0}$ = (0, 0, 0), $\textbf{k}_{1}$ = (1/2, 0, 0), $\textbf{k}_{2}$ = (0, 1/2, 1/2), $\textbf{k}_{3}$ = (1/2, 1/2, 1/2). The magnetic structure in the AF3 phase is incommensurate with $\textbf{k}_{AF3}$ = (0.5, $\delta$, 0). Our results are consistent with theoretical calculations based on crystal field theory.