1210.6689 (Onur Erten et al.)

Effective Spin Hamiltonian and Disorder Effects in Double Perovskite
Ferrimagnets    [PDF]

Onur Erten, O. Nganba Meetei, Anamitra Mukherjee, Mohit Randeria, Nandini Trivedi, Patrick Woodward

Double perovskites like Sr2FeMoO6 are materials with half-metallic ground states and ferrimagnetic Tc's well above room temperature. This paper is the second of our comprehensive theory for half metallic double perovskites. Here we derive an effective Hamiltonian for the Fe core spins by "integrating out" the itinerant Mo electrons. We next validate the classical spin Hamiltonian by comparing its results with those of the full quantum treatment presented in the companion paper "Double Exchange Mechanism for Half-metallic Double Perovskites". We then use it to compute magnetic properties as a function of temperature and disorder. We discuss the effect of excess Mo, excess Fe, and anti-site disorder on the magnetization and Tc. We conclude with a proposal to increase Tc without sacrificing carrier polarization.

View original: http://arxiv.org/abs/1210.6689