Magnetism in CaMnO3 thin films

Abstract

Epitaxial CaMnO3 thin films on (001) LaAlO3, (LaAlO3)0.3(Sr2AlTaO6)0.7, and SrTiO3 were synthesized in a range of strain states from coherently strained on LaAlO3 (1.6% strain) to fully relaxed on SrTiO3. We observed a magnetic ordering transition in CaMnO3 thin films suppressed from the Néel temperature of bulk CaMnO3 with the suppression increasing with increasing strain in the thin film. In contrast to bulk studies, our CaMnO3 films do not exhibit any sign of weak ferromagnetism according to field-dependent magnetization and x-ray magnetic circular dichroism measurements. Therefore, to within experimental resolution, all of our CaMnO3 films are antiferromagnetic with negligible oxygen off-stoichiometry.