Anomalous pressure effect on the magnetic ordering in multiferroic BiMnO3

TL;DR

This study investigates how pressure influences magnetic ordering in BiMnO3, revealing complex pressure-dependent magnetic phase transitions and the emergence of a secondary magnetic peak.

Contribution

It provides new insights into pressure-induced magnetic phase behavior in BiMnO3, highlighting the interplay between magnetic and orbital structures.

Findings

Ferromagnetic transition at ~100 K increases with magnetic field.

Pressure causes the main ferromagnetic peak to decrease and eventually disappear.

A secondary magnetic peak appears at 9-13 kbar and persists up to 16 kbar.

Abstract

We report the magnetic field dependent dc magnetization and the pressure-dependent (pmax ~ 16 kbar) ac susceptibilities Xp(T) on both powder and bulk multiferroic BiMnO3 samples, synthesized in different batches under high pressure. A clear ferromagnetic (FM) transition is observed at TC ~ 100 K, and increases with magnetic field. The magnetic hysteresis behavior is similar to that of a soft ferromagnet. Ac susceptibility data indicate that both the FM peak and its temperature (TC) decrease simultaneously with increasing pressure. Interestingly, above a certain pressure (9 ~ 11 kbar), another peak appears at Tp ~ 93 K, which also decreases with increasing pressure, with both these peaks persisting over some intermediate pressure range (9 ~ 13 kbar). The FM peak disappears with further application of pressure; however, the second peak survives until present pressure limit (pmax ~ 16 kbar). These features are considered to originate from the complex interplay of the magnetic and orbital structure of BiMnO3 being affected by pressure.