Magnetic dilution and domain selection in the XY pyrochlore antiferromagnet Er2Ti2O7

Below TN=1.1 K, the XY pyrochlore Er2Ti2O7 orders into a k=0 noncollinear, antiferromagnetic structure referred to as the ψ2 state. The magnetic order in Er2Ti2O7 is known to obey conventional three-dimensional (3D) percolation in the presence of magnetic dilution, and in that sense is robust to disorder. Recently, however, two theoretical studies have predicted that the ψ2 structure should be unstable to the formation of a related ψ3 magnetic …