Eur. Phys. J. Appl. Phys. 94, 30301 (2021)
https://doi.org/10.1051/epjap/2021200365

Regular Article

Sustained coherent epitaxy and role of oxygen vacancies in La_0.7Sr_0.3MnO_3−δ thin films grown on SrTiO₃ by sputtering

¹ Department of Physics, Polydisciplinary Faculty of Ouarzazate, Ibn Zohr University, B.P. 638, Ouarzazate 45000, Morocco
² Department of Electronic Science and Engineering, Kyoto University, Kyoto 615-8510, Japan

^* e-mail: m.lmouchter@uiz.ac.ma

Received: 28 November 2020
Received in final form: 24 February 2021
Accepted: 21 May 2021
Published online: 16 June 2021

Abstract

Ferromagnetic La_0.7Sr_0.3MnO_3−δ (LSMO) epitaxial thin films of single-crystal quality with very smooth surfaces are grown on SrTiO₃ (100) substrates by on-axis rf magnetron sputtering. We find that the resistivity and the spontaneous magnetization for these 180 nm thick films are nearly equal to those of single crystals after thermal annealing. On the other hand, the Curie temperature T_C is no higher than 270 K, a value far below the bulk one, which is quite unusual. As a clue to this riddle, we note a strong correlation between the lattice constant for these films and the amount of oxygen vacancies in the case of LSMO, an oxygen-nonstoichiometric oxide. From this, we conclude that the sustained coherent epitaxy takes place to match the lattice mismatch of 0.8% by incorporating a limited amount of oxygen vacancies, which relaxes the film in-plane stress while functions to significantly reduce T_C.