Canonical magnetic insulators with isotropic magnetoelectric coupling

Sinisa Coh, David Vanderbilt
2013 Physical Review B  
We have performed an exhaustive representation-theory-based search for the simplest structures allowing isotropic magnetoelectric coupling. We find 30 such structures, all sharing a common pattern of atomic displacements in the direction of atomic magnetic moments. We focus on one of these 30 canonical structures and find that it is generically realized in a class of fractionally substituted pyrochlore compounds with an all-in-all-out magnetic order. Furthermore, we find that these substituted
more » ... yrochlore compounds have a substantial Chern-Simons orbital magnetoelectric component (\theta=0.1--0.2). While this component is also formally present in strong Z_2 topological insulators (\theta=\pi), its effects are observable there only if time-reversal symmetry is broken at the surface.
doi:10.1103/physrevb.88.121106 fatcat:23yhp2uj4fe3thv2256mv7f6wq