Magnetic order in YbMnO$_3$ studied by Neutron Diffraction and M\"ossbauer Spectroscopy

TL;DR

This study investigates the magnetic ordering in YbMnO$_3$ using neutron diffraction and M"ossbauer spectroscopy, revealing distinct ordering temperatures for Yb and Mn moments and proposing a model for their interactions.

Contribution

It provides new insights into the temperature-dependent magnetic ordering of Yb and Mn in YbMnO$_3$, highlighting the different ordering temperatures and interaction mechanisms.

Findings

Yb moments at 4b site order with Mn moments at 85 K.

Yb moments at 2a site order below 3.5 K.

A molecular field model explains the temperature dependence of magnetic moments.

Abstract

The magnetic ordering of the hexagonal multiferroic compound YbMnO$_3$ has been studied between 100 K and 1.5 K by combining neutron powder diffraction, $^{170}$Yb M\"ossbauer spectroscopy and magnetization measurements. The Yb moments of the two crystallographic sites order at two different temperatures, the $4b$ site together with the Mn moments (at $T_N \simeq$85 K) and the $2a$ site well below (at 3.5 K). The temperature dependences of the Mn and Yb moments are explained within a molecular field model, showing that the $4b$ and $2a$ sites order via Yb-Mn and Yb-Yb interactions respectively. A simple picture taking into account the local Mn environment of the Rare earth R ($4b$) ion is proposed to couple R and Mn orders in hexagonal RMnO$_3$ manganites. The nature and symmetry of the R-Mn interactions yielding the R order are discussed.