X-ray Absorption Spectroscopy Study of Thickness Effects on the Structural and Magnetic Properties of Pr2−δNi1−xMn1+xO6−y Double Perovskite Thin Films

Abstract

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 Pr2−δNi1−xMn1+xO6−y (PNMO) double perovskite grown on top of two different (001)-SrTiO3 and (001)-LaAlO3 substrates by RF magnetron sputtering. A strong dependence of the structural and magnetic properties on the film thickness is found. The ferromagnetic transition temperature (TC) 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 Ni2+ and Mn4+, thus the ferromagnetism is mainly due to Ni2+-O-Mn4+ 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.

Impact of thermal gas treatment on the surface modification of Li-rich Mn-based cathode materials for Li-ion batteries

“…The Mn 3+ and Mn 7+ states were treated with D 4h symmetry to account for Jahn–Teller distortion, while the Mn 2+ and Mn 4+ states were considered to have octahedral ( O h ) symmetry. 75,76 The Mn L 3,2 edge of Mn 7+ was shifted by 4.9 eV to lower photon energies for the peak position at 645 eV in accordance with the experimental data, ref. 31 The parameters used for the simulations are outlined in Table S1, ESI †.…”