Ferroelectric and Magnetic SrTiCoO3 films on Silicon and Niobium-doped SrTiO3 substrates

Perovskites hold great potential for fundamental studies of structure-multiferroicity relationship as well as technological applications such as multi-level memories. We demonstrate multiferroic behavior of Cobalt-substituted SrTiO3 (STCo) films on Silicon and on Niobium-doped SrTiO3 substrates (Nb:STO). STCo films were grown on Si, silicon-on-insulator, Nb:STO, 3 $\mu $m thick SiO2 coated Si, and pure STO substrates using pulsed laser deposition under different oxygen pressures (1, 3, 6 $\mu $Torr, 1.6 mTorr). The film composition is SrTi0.70Co0.30O3-$\delta $, as confirmed by $\omega $-2$\theta $ scans of x-ray difractometer. Magnetic hysteresis loops indicate that the films have out-of-plane easy axis with anisotropy field of several kOe, which is attributed to magnetoelastic anisotropy. Saturation magnetizations of 0.9, 0.3, 0.5 and 0.2 $\mu $B/Co ion were obtained for samples grown on Nb:STO under oxygen pressures 1, 3, 6 $\mu $Torr, 1.6 mTorr, respectively. Ferroelectric saturation polarizations of 67 to 118 $\mu $C/cm2 and resistivities between 1e6 to 1e9 $\Omega \cdot$ cm were obtained for STCo on Nb:STO and on Silicon. The origin of the magnetic and ferroelectric properties will be discussed.