Tuning magnetic properties with off-stoichiometry in oxide thin films: An experiment with yttrium iron garnet as a model system

Abstract

We demonstrate how controlled changes in oxygen stoichiometry tune the magnetic properties and the superexchange interaction, thus providing a simple and efficient method to elaborate magnetic oxides with strongly modified magnetic and semiconductor properties. Structural and magnetic properties of the model system of yttrium iron garnet (YIG) thin films were tuned by controlling oxygen stoichiometry. The YIG phase diagram has been explored by creating cation and oxygen vacancies during film growth by pulsed laser deposition. Especially, unexplored in thermodynamic equilibrium growth conditions, excess oxygen stoichiometry in a YIG unit cell was investigated: a significant increase of Curie temperature $(+10%)$ and magnetization $(+20%)$ were observed. These changes are understood in the framework of a microscopic model implying the formation of ${\mathrm{Fe}}^{4+}$ and ${\mathrm{Fe}}^{2+}$ in the films with oxygen excess and vacancies, respectively.