Non-collinear Magnetic Order in the Double Perovskites: Double Exchange on a Geometrically Frustrated Lattice

Abstract

Double perovskites of the form A_2BB'O_6 usually involve a transition metal ion, B, with a large magnetic moment, and a non magnetic ion B'. While many double perovskites are ferromagnetic, studies on the underlying model reveal the possibility of antiferromagnetic phases as well driven by electron delocalisation. In this paper we present a comprehensive study of the magnetic ground state and T_c scales of the minimal double perovskite model in three dimensions using a combination of spin-fermion Monte Carlo and variational calculations. In contrast to two dimensions, where the effective magnetic lattice is bipartite, three dimensions involves a geometrically frustrated face centered cubic (FCC) lattice. This promotes non-collinear spiral states and `flux' like phases in addition to collinear anti-ferromagnetic order. We map out the possible magnetic phases for varying electron density, `level separation' epsilon_B - epsilon_B', and the crucial B'-B' (next neighbour) hopping t'.

15 pages pdflatex + 19 figs, revision: removed redundant comments

References in corpus (4)

• Electronic Structure, Phonons and Dielectric Anomaly in Ferromagnetic Insulating Double Perovskite La2NiMnO6
• Magnetic and electric properties of double-perovskites and estimation of their Curie temperatures by ab initio calculations
• Signature of an antiferromagnetic metallic ground state in heavily electron doped Sr2FeMoO6
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