Ferromagnetic response of multiferroic TbMnO3 films mediated by epitaxial strain and chemical pressure

High quality Tb1-xAlxMnO3 (x = 0, 0.3) films have been grown under different values of compressive/tensile strain using (001)-oriented SrTiO3 and MgO substrates. The films were grown by means of rf sputtering at substrate temperature of 800 degrees C. X-ray diffraction analysis shows that films are single phase, preferentially oriented in the (111) and (122) directions for films deposited on SrTiO3 and MgO substrates, respectively. Although the TbMnO3 target shows antiferromagnetic order, the films deposited on both substrates show weak ferromagnetic phase at low temperature coexisting with the antiferromagnetic phase. The introduction of Al in the films clearly enhances their ferromagnetic behavior, improving the magnetic performance of this material. Indeed, M(H) measurements at 5 K show a well-defined hysteresis for films grown on both substrates. However, a stronger magnetic signal (larger values of remanence and coercive field) is observed for films deposited on MgO substrates. The chemical pressure generated by Al doping together with the substrate-induced strain seem to modify the subtle competition between magnetic interactions in the system. It is speculated that such modification could lead to a non-collinear magnetic state that may be tuned by strain modifications. This may be performed by varying the thickness of the films and/or considering other substrate materials. (C) 2014 AIP Publishing LLC.