Continuous Collapse of the Spin Cycloid in BiFeO3 Thin Films under an Applied Magnetic Field probed by Neutron Scattering

TL;DR

This study demonstrates that applying a high magnetic field can systematically suppress the spin cycloid in BiFeO3 thin films, revealing potential for tunable multiferroic properties in future spintronic applications.

Contribution

It provides experimental evidence that a magnetic field can control the spin cycloid in BiFeO3 thin films, with lower critical fields than in bulk, enabling new functionalities.

Findings

Spin cycloid can be suppressed by a 10 T magnetic field.

Critical magnetic field for thin films is lower than for bulk crystals.

Spin cycloid expands with increasing magnetic field before suppression.

Abstract

Bismuth ferrite (BiFeO3) is one of the rare materials that exhibits multiferroic properties already at room-temperature. Therefore, it offers tremendous potential for future technological applications, such as memory and logic. However, a weak magnetoelectric coupling together with the presence of a noncollinear cycloidal spin order restricts various practical applications of BiFeO3. Therefore, there is a large interest in the search for suitable methods for the modulation of the spin cycloid in BiFeO3. By performing neutron diffraction experiments using a triple-axis instrument we have determined that the spin cycloid can be systematically suppressed by applying a high magnetic field of 10 T in a BiFeO3 thin film of about 100 nm grown on a (110)-oriented SrTiO3 substrate. As predicted by previous theoretical calculations, we observed that the required critical magnetic field to suppress the spin cycloid in a BiFeO3 thin film was lower as compared to the previously reported critical magnetic field for bulk BiFeO3 single crystals. Our experiment reveals that the spin cycloid continuously expands with increasing magnetic field before the complete transformation into a G-type antiferromagnetic spin order. Such tuning of the length of the spin cycloid up to a complete suppression offers new functionalities for future technological applications as in spintronics or magnonics.