Magnetic anisotropy and valence states in La$_2$Co$_{1-x}$Mn$_{1+x}$O$_6$ ($x\approx 0.23$) thin films studied by X-ray absorption spectroscopy techniques

TL;DR

This study uses X-ray absorption spectroscopy to analyze valence states and magnetic anisotropy in La$_2$Co$_{1-x}$Mn$_{1+x}$O$_6$ thin films, revealing strain-dependent magnetic properties and the origin of anisotropy.

Contribution

It provides new insights into the valence states and magnetic anisotropy mechanisms in non-stoichiometric La$_2$Co$_{1-x}$Mn$_{1+x}$O$_6$ thin films, supported by experimental and theoretical analysis.

Findings

Co is in a divalent state despite non-stoichiometry

Mn ions exhibit a mixed valence state

Magnetic anisotropy depends on strain and originates from Co spin-orbit coupling

Abstract

X-ray absorption spectroscopy was used to determine the valence state in La$_2$Co$_{1-x}$Mn$_{1+x}$O$_6$ ($x\approx 0.23$) thin films. We found that in spite of the non-stoichiometry, Co is in a divalent state while Mn ions show a mixed valence state. The relation of this finding with the magnetic properties of the films is discussed. X-ray magnetic circular dichroism measurements prove that magnetic anisotropy originates from Co spin-orbit coupling and it is strain-dependent: a strong increase of the angular contribution to the magnetic moment is found when in-plane (out-of-plane) and cell parameters get expanded (compressed). This behavior is reproduced by first order perturbation theory calculations.