Field induced changes in cycloidal spin ordering and coincidence between magnetic and electric anomalies in BiFeO3 multiferroic

TL;DR

This study investigates how magnetic fields induce changes in the cycloidal spin structure of BiFeO3, revealing a correlation between magnetic and electric anomalies near the Néel temperature, and identifies field-induced spin transitions.

Contribution

It provides detailed experimental evidence of field-induced spin structure transitions in BiFeO3 and links magnetic anomalies with electric property changes near the phase transition.

Findings

Field-induced transition from circular to anharmonic cycloid at H=Ha

Cycloid vanishes at H=Hc, leading to linear magnetization

Coincidence of magnetic and electric anomalies near TN

Abstract

The ZFC and FC magnetization dependence on temperature was measured for BiFeO3 ceramics at the applied magnetic field up to H=10T in 2K-1000K range. The antiferromagnetic order was detected from the hysteresis loops below the Neel temperature TN=646K. In the low magnetic field range there is an anomaly in M(H), probably due to the field-induced transition from circular cycloid to the anharmonic cycloid. At high field limit we observe the field-induced transition to the homogeneous spin order. From the M(H) dependence we deduce that above the field Ha the spin cycloid becomes anharmonic which causes nonlinear magnetization, and above the field Hc the cycloid vanishes and the system again exhibits linear magnetization M(H). The anomalies in the electric properties, which are manifested within the 640K-680K range, coincide to the anomaly in the magnetization M(T) dependence, which occurs in the vicinity of TN. We propose to ascribe this coincidence to the critical behaviour of the chemical potential, related to the magnetic phase transition.