Abstract
Motivated by experiments on the double perovskites and , we study the magnetism of spin-orbit coupled iridium moments on the three-dimensional, geometrically frustrated, face-centered cubic lattice. The symmetry-allowed nearest-neighbor interaction includes Heisenberg, Kitaev, and symmetric off-diagonal exchange. A Luttinger-Tisza analysis shows a rich variety of orders, including collinear -type antiferromagnetism, stripe order with moments along the direction, and incommensurate noncoplanar spirals, and we use Monte Carlo simulations to determine their magnetic ordering temperatures. We argue that existing thermodynamic data on these iridates underscores the presence of a dominant Kitaev exchange, and also suggest a resolution to the puzzle of why , but not , exhibits “weak” ferromagnetism.
- Received 5 February 2015
- Revised 9 July 2015
DOI:https://doi.org/10.1103/PhysRevB.92.020417
©2015 American Physical Society