InMnO3 : a fully frustrated multiferroic

TL;DR

This paper investigates InMnO3, a unique hexagonal manganite with unusual magnetic and electronic properties, revealing a fully frustrated multiferroic behavior with complex magnetic ordering driven by pseudo-dipolar interactions.

Contribution

The study provides detailed neutron diffraction analysis of InMnO3, demonstrating its fully frustrated multiferroic nature and identifying the role of pseudo-dipolar interactions in its magnetic structure.

Findings

Magnetic order appears below 120 K with a doubled magnetic unit cell.

Short-range two-dimensional spin correlations exist above the ordering temperature.

Mn ions are positioned near the threshold for superexchange interactions along the c-axis.

Abstract

InMnO$_3$ is a peculiar member of the hexagonal manganites h-RMnO$_3$ (where R is a rare earth metal element), showing crystalline, electronic and magnetic properties at variance with the other compounds of the family. We have studied high quality samples synthesized at high pressure and temperature by powder neutron diffraction. The position of the Mn ions is found to be close to the threshold $\it{x}=1/3$ where superexchange Mn-Mn interactions along the $\it{c}$ axis compensate. Magnetic long range order occurs below $T_{\rm N}$= 120(2) K with a magnetic unit cell doubled along $\it{c}$, whereas short range two dimensional dynamical spin correlations are observed above $T_{\rm N}$. We propose that pseudo-dipolar interactions are responsible for the long period magnetic structure.