Modified surface electronic and magnetic properties of La _0.6Sr_0.4MnO₃ thin films for spintronics applications

We present the surface electronic and magnetic properties of half-metal La_0.6Sr_0.4MnO₃ (LSMO) thin film modified by a simple cleaning procedure, the so-called SC1 (5 H₂O, 1 NH ₄OH, 1 H₂O₂), at 85 °C for 10-40 min in ambient atmosphere. In this study, photoemission spectroscopy (XPS/UPS), X-ray absorption spectroscopy (XAS), and X-ray magnetic circular dichroism (XMCD) are used to characterize these properties of the manganites. Thanks to SC1 treatment, the work function of LSMO changes from 4.0-4.1 to 4.8-4.9 eV obtained from UPS measurements, while its surface roughness changes from 0.268 to 0.796 nm in AFM images. Combined O 1s, Mn 2p, Sr 3d, La 4d, and Mn 3s core-level XPS spectroscopy investigations suggest that Mn and Sr contents decrease at the surface and the Mn value becomes 3.7 due to SC1 treament. Mn L-edge XAS spectra of LSMO thin film demonstrate that SC1 treatment results in a removal of Mn ²⁺ and an increase of the Mn⁴⁺ concentration. O K-edge XAS spectra further prove an enhancement of hybridization between O 2p orbitals and e_g of Mn 3d induced by more Mn⁴⁺. XMCD results show that SC1 treatment does not induce any drastic changes of magnetic properties of the LSMO thin film surface.