The Spin-Reorientation Transition in TmFeO3

TL;DR

This study uses advanced x-ray techniques to investigate the magnetic behavior of TmFeO3 during its spin reorientation transition, revealing surface effects and complex interactions between Fe and Tm magnetic moments.

Contribution

It provides new insights into the surface-enhanced SRT and the limitations of dipolar mean field models in describing the 4f magnetic response.

Findings

Surface region shows an extended temperature range for SRT.

Induced magnetic moments on Tm sites are observed and modeled.

Decoupling of spin canting and spin rotation near the surface is indicated.

Abstract

X-ray magnetic circular and linear dichroism (XMCD and XMLD) have been used to investigate the Fe magnetic response during the spin reorientation transition (SRT) in TmFeO3. These experiments are complemented with resonant magnetic diffraction experiments at the Tm M5 edge to study simultaneously the induced magnetic order in the Tm 4f shell and the behavior of the Tm orbitals through the SRT. Comparing the Fe XMLD results with neutron diffraction and magnetization measurements on the same sample indicate that the SRT has an enhanced temperature range in the near surface region. This view is supported by the resonant soft x-ray diffraction results at the Tm M5 edge. These find an induced magnetic moment on the Tm sites, which is well-described by a dipolar mean field model originating from the Fe moments. Even though such a model can describe the 4f response in the experiments, it is insufficient to describe the SRT even when considering a change in the 4f anisotropy. Moreover, the results of the Fe XMCD are indicative of a decoupling of spin canting and antiferromagnetic spin rotation in the near surface regime close to the SRT, which remains to be understood.