Influence of Fe substitution on the Jahn-Teller distortion and orbital anisotropy in orthorhombic Y(Mn1-xFex)O3 epitaxial films

Multiferroic YMn1−xFexO3(020) (x = 0.125, 0.25, 0.50) epitaxial thin films with an orthorhombic structure (space group Pbnm) were prepared on a YAlO3(010) substrate by pulsed-laser deposition. Upon Fe substitution, the b-axis was clearly shortened, whereas the a- and c-axes were slightly lengthened based on XRD analysis. To understand the influence of orbital polarization and the Jahn–Teller effect of Mn3+ on Fe substitution and also the local octahedral-site distortion of Fe3+ in an environment of Jahn–Teller-active Mn3+ ions in YMn1−xFexO3 films, we measured the polarization-dependent X-ray absorption spectra at the Mn-L2,3 and Fe-L2,3 edges, and also simulated the experimental spectra using configuration-interaction multiplet calculations. Although Δeg for the Mn3+ ion decreased from 0.9 eV in pure YMnO3 to 0.6 eV in the half-Fe-substituted sample, a single eg electron was still strongly constrained to the d3y2−r2 orbital for all the Fe concentrations tested. The largest Δeg, 0.5 eV, for the Fe3+ ion was derived for a sample with 12.5% Fe substitution, and gradually decreased to 0.15 eV for the half-Fe-substituted sample. The local octahedral-site distortion of the Fe3+ ion inside the YMnO3 lattice was similar to that of the Mn3+ ion, whereas the Jahn–Teller distortion and GdFeO3-type distortion of the Mn3+ ion were decreased by the spherical high-spin Fe3+ ions. The combination of the experimental and theoretical data provides both profound insight into the variation of the Jahn–Teller distortion and orbital anisotropy and instructive information about the magnetic structures in these orthorhombic YMn1−xFexO3 thin films.