The electronic and magnetic properties of strained La_0.85Zr_0.15MnO₃ films

The electronic and magnetic properties of strained tetravalent-ion-doped La0.85Zr0.15MnO3 (LZMO) thin films that were epitaxially grown on SrTiO3 (STO) and MgO substrates were studied using temperature-dependent x-ray diffraction (XRD), x-ray absorption near-edge structure (XANES), x-ray linear dichroism (XLD) and x-ray magnetic circular dichroism (XMCD) at the Mn L3,2- and K-edge. XRD studies reveal that the LZMO thin films have compressive and tensile strains on the STO and MgO substrates, respectively. As temperature is reduced from room temperature to below magnetic transition temperature, the preferentially occupied Mn majority-spin eg orbital changes from the in-plane dx2-y2 to the out-of-plane d3z2-r2 orbital for LZMO/STO, and vice versa for LZMO/MgO. Experimental results suggest that the new hopping path that is mediated by the Mn2+ ions triggers a stronger d3z2-r2 orbital ordering of Mn3+ ions and enhances the ferromagnetic coupling between the Mn spin moments of t2g electrons in LZMO/STO, whereas the tensile strain stabilizes the dx2-y2 orbital by inducing lattice distortions of the MnO6 octahedra in LZMO/MgO.

X-ray Absorption Spectroscopic studies of Single Crystal SrFeO_3-δ

We have prepared a high quality single crystal of SrFeO3-δ (δ ~ 0.14) by the floating-zone method to study the electronic and atomic structures using temperature-dependent x-ray absorption near-edge structure (XANES), x-ray linear dichroism (XLD), and extended x-ray absorption fine structure (EXAFS) at the O K-edge, Fe L3,2- and K-edge. Resistivity measurements indicate that the SrFeO2.86 shows an anisotropic behavior, and thermal hysteresis behavior between 70 K and 40 K. The temperature dependent Fe K-edge EXAFS studies shows that the Fe-O bond length changes in ab-plane below transition temperature. The XLD results illustrate that as temperature is reduced from room temperature to below the transition temperature, the preferential occupancy of Fe majority-spin eg orbitals changes from the 3d3z2-r2 to 3dx2-y2, but restore to 3dx2-y2 after thermal hysteresis. Experimental findings suggest that the charge transfer during thermal hysteresis is induced by lattice distortions of the FeO6 octahedra in SrFeO2.86.