Theory of Half-Metallic Double Perovskites II: Effective Spin Hamiltonian and Disorder Effects

Abstract

Double perovskites like Sr${}_2$FeMoO${}_6$ are materials with half-metallic ground states and ferrimagnetic T${}_{\mathrm{c}}$'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 and obtain an unusual double square-root form of the spin-spin interaction. We validate the classical spin Hamiltonian by comparing its results with those of the full quantum treatment presented in the companion paper "Theory of Half-Metallic Double Perovskites I: Double Exchange Mechanism". We then use the effective Hamiltonian to compute magnetic properties as a function of temperature and disorder and discuss the effect of excess Mo, excess Fe, and anti-site disorder on the magnetization and T${}_{\mathrm{c}}$. We conclude with a proposal to increase T${}_{\mathrm{c}}$ without sacrificing carrier polarization.

References in corpus (11)

• Electronic Structure of Sr_2FeMoO_6
• Exotic phases induced by strong spin-orbit coupling in ordered double perovskites
• Spin-orbit coupling in $d^2$ ordered double perovskites
• Theory of Half-metallic Ferrimagnetism in Double Perovskites
• Theory of Half-Metallic Double Perovskites I: Double Exchange Mechanism
• Theory of High T${}_c$ Ferrimagnetism in a Multi-orbital Mott Insulator
• Phase diagram and influence of defects in the double perovskites
• A Magnetic Model for the Ordered Double Perovskites
• Metal-insulator transition in the double perovskites
• Hidden Symmetries and their Consequences in $t_{2g}$ Cubic Perovskites
• Effective three-band model for double perovskites

Cited by in corpus (6)

• Theory of Half-Metallic Double Perovskites I: Double Exchange Mechanism
• Possible Half Metallic Antiferromagnetism in a Double Perovskite Material with Strong Spin-Orbit Couplings
• Understanding the Magnetic Puzzles of Double Perovskites A2FeOsO6 (A=Ca, Sr)
• Theory of metallic double perovskites with spin orbit coupling and strong correlations; application to ferrimagnetic Ba2FeReO6
• Tuning the probability of defect formation via substrate strains in Sr${}_2$FeMoO${}_6$ films
• First-principles analysis of the effect of magnetic states on the oxygen vacancy formation energy in doped La${}_{0.5}$Sr${}_{0.5}$CoO${}_3$ perovskite