X-ray Absorption Spectroscopy Study of Thickness Effects on the Structural and Magnetic Properties of Pr(2−δ)Ni(1−x)Mn(1+x)O(6−y) Double Perovskite Thin Films

In this work, we report a systematic study of the influence of film thickness on the structural and magnetic properties of epitaxial thin films of Pr(2−δ)Ni(1−x)Mn(1+x)O(6−y) (PNMO) double perovskite grown on top of two different (001)-SrTiO(3) and (001)-LaAlO(3) substrates by RF magnetron sputtering. A strong dependence of the structural and magnetic properties on the film thickness is found. The ferromagnetic transition temperature (T(C)) and saturation magnetization (Ms) are found to decrease when reducing the film thickness. In our case, the thinnest films show a loss of ferromagnetism at the film-substrate interface. In addition, the electronic structure of some characteristic PNMO samples is deeply analyzed using X-ray absorption spectroscopy (XAS) and X-ray magnetic circular dichroism (XMCD) measurements and compared with theoretical simulations. Our results show that the oxidation states of Ni and Mn ions are stabilized as Ni(2+) and Mn(4+), thus the ferromagnetism is mainly due to Ni(2+)-O-Mn(4+) superexchange interactions, even in samples with poor ferromagnetic properties. XMCD results also make evident large variations on the spin and orbital contributions to the magnetic moment as the film’s thickness decreases.