Tuning of magnetism in SrRuO3 thin films on SrTiO3 (001) substrate by control of the twin and strain amount in the buffer layer

Control of the magnetic easy axis in SrRuO3 thin films is important for tunnel junction studies incorporating this layer and for wider device applications. Previously, we demonstrated control of the magnetic easy axis in SrRuO3 thin films on SrTiO3 (110) substrates by introducing tunable anisotropic strain through a CaHfO3 buffer layer. However, our method was not directly applicable due to the existence of twins in the CaHfO3 layer that grew on the SrTiO3 (001) substrate. Twins appeared partly because of the crystal structure of CaHfO3, which has large orthorhombic distortion (a-b)/a=2.5%. Here, we used a miscut SrTiO3 (001) substrate to create a twin-free CaHfO3 layer on the substrate, even though the large mismatch between the CaHfO3 and SrTiO3 (001) substrates led to relaxed growth behavior. The crystal quality of the CaHfO3 layer, as determined by the shape of the rocking curve and existence of twins, was markedly improved by use of the miscut substrate. In addition, the SrRuO3 film grown on top of this buffer layer was of high quality and tensile strain and had an in-plane magnetic easy axis.