Unusual ferromagnetic YMnO₃ phase in YMnO₃/La_2 / 3Sr_1 / 3MnO₃ heterostructures

By means of first-principles density functional calculations, we study the structural, magnetic and electronic properties of YMnO₃/La_2/3Sr_1/3MnO₃ heterostructures. Although in the bulk the ground state of YMnO₃ is an antiferromagnet, the YMnO₃/La_2/3Sr_1/3MnO₃ heterostructure stabilizes the ferromagnetic (FM) phase in YMnO₃ in the interface region over a wide range of Coulomb repulsion parameters. The hypothetical FM phase of bulk YMnO₃ is dielectric and due to substantial differences between the lattice constants in the ab plane, a strong magnetocrystalline anisotropy is present. This anisotropy produces a high coercivity of the unusual FM YMnO₃ that can explain the large vertical shift in the hysteresis loops observed in recent experiments (Paul et al 2014 J. Appl. Crystallogr. 47 1054). The correlation between weak exchange bias and the vertical shift is proposed, which calls for reinvestigation of various systems showing vertical shifts. (paper)