Magnetic Anisotropy in Epitaxial SrRuO$_3$ and Ba$_{0.5}$Sr$_{0.5}$RuO$_3$ on (001) SrTiO$_3$ substrates

Epitaxial thin films exhibit quite different properties from the corresponding bulk materials due to strain induced by the substrate. For instance, a bulk SrRuO$_{3}$ (SRO) single crystal, has a Curie temperature near 160K with two magnetic easy axis. However, there shows unianxial magnetic anisotropy in single domain epitaxial SRO grown on SrTiO$_{3}$ (STO) substate[1]. In this study, we have grown epitaxial SRO and Ba$_{0.5}$Sr$_{0.5}$RuO$_{3}$ (BSRO) on 4$^{\circ}$ miscut (001) STO substrates using pulsed laser deposition (PLD) with in-situ high pressure reflection high energy electron-diffraction (RHEED). Through detailed X-ray diffraction, magnetization and angle-dependent magneto-transport measurements, we explore the magnetic properties of SRO and BSRO. However, in contrast to non-magnetic properties of bulk BSRO and uniaxial anisotropy in SRO film, BSRO film shows ferromagnetism with Tc about 140K and non-uniaxial properties. We discuss the mechanism in terms of lattice distortion due to strain effect and spin-orbit coupling. 1] Q. Gan, R. A. Rao, C. B. Eom, L. Wu, and F. Tsui, J. Appl. Phys. \textbf{85}, 5297 (1999).