Evidence of Ferromagnetic Response of TbMnO3 Thin Films at High Temperatures

Magnetometry measurements performed on TbMnO films grown onto single-crystal [001] SrTiO substrates using magnetron sputtering technique exhibit series of anomalies related to the magnetic ordering of the Mn sublattice. Despite the fact that bulk TbMnO is a low-temperature antiferromagnet, the measurements indicate the presence of high-temperature ferromagnetism. Well-defined hysteresis loops are observed at temperatures as high as 70 K. Analysis of the X-ray diffraction patterns of the target and films shows no evidence of affectation (within the resolution limit of the technique) by external impurities, such as MnO, which might give rise to an artificial magnetic signal. Thus, it is probable that the ferromagnetism observed in the films to be an intrinsic property of TbMnO. Concretely, it is possible that the strain imposed by the substrate, resulting in the tetragonally distorted orthorhombic phase of the TbMnO films, is behind the mechanism governing the anomalous ferromagnetism observed in the films.