The wasp-waisted hysteresis loop and exchange bias in multiferroic BaNiF4

Shuang Zhou,Jun Du,Qingyu Xu,Ji Wang

doi:10.1063/1.4977503

Abstract

Multiferroic BaNiF4 has been fabricated by hydrothermal method. The bifurcation between zero field cooling (ZFC) and field cooling (FC) temperature dependent magnetization (M-T) curves starts at 150 K, indicating the 2D antiferromagnetic (FM) transition. A further upturn of magnetization has been observed below 68 K in FC M-T curve, corresponding to the emergence of 3D AFM structure. Wasp-waisted hysteresis loop was observed under 130 K, which is explained by that the AFM aligned net spins from the canting of neighboring AFM spins due to Dzyaloshinskii-Moriya interaction can be easily aligned by the magnetic field. Exchange bias effect was detected below 70 K, which has been interpreted by the magnetization pinned by the spontaneous polarization through magnetoelectric coupling.

Highlights

In the past decades, most research attentions on multiferroics have been focused on various transition metal oxides.[1,2,3] Besides the great progress on multiferroic oxides, there are still some disadvantages of these materials, such as low working temperatures and weak polarization/magnetization, which prevents their immediate applications
Our results provide the evidence of weak AFM in BaNiF4 and the easy alignment of net spins due to canting, which sheds light on the possible magnetoelectric applications
BaNiF4 powder were synthesized by low-temperature hydrothermal method

Summary

INTRODUCTION

Most research attentions on multiferroics have been focused on various transition metal oxides.[1,2,3] Besides the great progress on multiferroic oxides, there are still some disadvantages of these materials, such as low working temperatures and weak polarization/magnetization, which prevents their immediate applications. Room-temperature spontaneous polarization was reported to be 6.7 μC cm-2 along c axis due to the displacement of Ba2+ ions, which is quite different from the mechanism in ferroelectric oxides that octahedra are the major contributors to the ferroelectric polarization.[8] The magnetic structure consists of puckered (010) sheets, within each sheet the magnetic cations form a puckered rectangular grid. These intralayer exchange interactions are probably quite strong, since they involve Ni-F-Ni configurations which are not far from being linear. BaNiF4 powder were fabricated by using a hydrothermal method, the detailed structure and magnetic properties were investigated

EXPERIMENTAL

RESULTS AND DISCUSSION

CONCLUSIONS