Structure, magnetic properties and magnetoelastic anisotropy in epitaxial Sr(Ti₁₋ₓCoₓ)O₃ films

Abstract

We report the structure, magnetic properties and magnetoelastic anisotropy of epitaxial Sr(Ti₁₋ₓCoₓ)O₃ films grown on LaAlO₃ (001) and SrTiO₃ (001) substrates by pulsed laser deposition. Room temperature ferromagnetism was observed in the Sr(Ti[subscript 0.86]Co[subscript 0.14])O₃ and Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ films. The formation of magnetic secondary phases such as Co-metal clusters in Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ is excluded based on x-ray diffraction, cross-sectional TEM, x-ray photoelectron spectroscopy and x-ray-absorption near edge spectroscopy. A large magnetic anisotropy is observed in Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ films. The net anisotropy is strongly influenced by growth conditions and the substrate and is attributed to magnetoelastic effects. The magnetoelastic anisotropy is related to the valence and spin states of the Co ions, which contribute to the ferromagnetic properties. Magneto-optical characterization yields a figure of merit (Faraday rotation/optical absorption) of 0.57 deg dB⁻[superscript 1] in the Sr(Ti[subscript 0.77]Co[subscript 0.23])O₃ film at 1550 nm wavelength, making it potentially useful in integrated magneto-optical applications.