Unconventional magnetism in 2D triangular antiferromagnets

Andrey V Chubukov - University of Minnesota, Minneapolis, USA

I will discuss new phases in 2D antiferromagnets on a triangular lattice in a magnetic field. A system with isotropic nearest neighbour interaction is known to undergo a set of phase transitions with increasing field and to possess, in a finite field range, an “up-up-down” phase with magnetization plateau at exactly 1/3 of the saturation value. I discuss how this phase and the states around it evolve when (i) the nearest neighbour interaction becomes anisotropic (as in Cs2CuCl4 and Cs2CuBr4), and (ii) when second neighbor exchange interaction becomes sizable. For the first model, I discuss incommensurate phases around the up-up-down phase and how this phase eventually collapses at large anisotropy. For the second model, I argue that when the second neighbor exchange exceeds a critical value, the “up-up-down” phase disappears, but instead the system develops a novel “up-up-up-down” phase with magnetization plateau at exactly 1/2 of the saturation value.

Host: Dr Amalia Coldea

Audrey Wood Seminar Room, Clarendon Laboratory