Ferromagnetism in epitaxial orthorhombic YMnO3 thin films

Epitaxial orthorhombic YMnO3 thin films, (001) oriented, have been grown by pulsed laser deposition on (001) SrTiO3 substrates. Their crystal structure and magnetic response have been studied in detail. Although bulk o-YMnO3 is antiferromagnetic, our magnetic measurements reveal intriguing thermal hysteresis between the zero-field-cooled and field-cooled curves below the onset of the antiferromagnetic ordering temperature, thus signaling a more complex magnetic structure with net ferromagnetic moments. We discuss on the possible origin of this net magnetization and we have found a correlation of the magnetic response with the strain state of the films. We propose that substrate-induced strain modifies the subtle competition of magnetic interactions and leads to a non-collinear magnetic state that can thus be tuned by strain engineering. (C) 2009 Elsevier B.V. All rights reserved.