Magnetic and magneto-optical properties of films of multiferroic GdMnO3 grown on LSAT [(LaAlO3)0.3 (Sr2AlTaO6)0.7] (100) and (111)

The magnetic properties of multiferroic GdMnO3 depend on strain which is produced in a thin film by growing an epitaxial film on a suitable substrate. We report an investigation of the magnetic and optical properties of GdMnO3, as a function of strain, produced by growing epitaxial films on the substrates on (LaAlO3)0.3(Sr2AlTaO6)0.7 (LSAT) (100) and (111). Magnetic measurements have shown that at 5 K the easy direction of the film is in-plane for LSAT (100) and the canted moment is significantly smaller than the value found in bulk material but larger than that found for GdMnO3 on SrTiO3 (100). The coercive field of the GdMnO3/LSAT (100) has also been found to be smaller than for bulk single crystal samples but comparable to a thinner film of GdMnO3 grown on SrTiO3. The magnetic properties of the film grown on LSAT (111) are very different. The transition to the canted phase is less pronounced and there is no magnetic hysteresis at low temperatures. The susceptibility data are fitted with the Curie's law and the measured magnetic moments for the film on LSAT (100) were similar to bulk values but significantly different for films on LSAT (111) and SrTiO3 (100). The magnetic circular dichroism spectroscopy showed two features: the charge transfer transition between Mn d states at ~ 2 eV and the band edge transition from the oxygen p band to the d states at ~ 3 eV. Magnetic circular dichroism also shows that the transition at around 2 eV is stronger in LSAT (100) than in LSAT (111) implying that the structure of the film of GdMnO3 is closer to that of LaMnO3 when grown on LSAT (100).