Ground state selection in XY pyrochlore antiferromagnets R $ _ {2} $ Ge $ _ {2} $ O $ _ {7} $(R= Er, Yb)

摘要: Elastic neutron scattering, ac susceptibility, and specific heat experiments on the pyrochlores ErGeO and YbGeO show that both systems are antiferromagnetically ordered in the manifold. The ground state is a phase for the Er sample and a or phase for the Yb sample, which suggests "Order by Disorder"(ObD) physics. Furthermore, we unify the various magnetic ground states of all known RBO (R = Er, Yb, B = Sn, Ti, Ge) compounds through the enlarged XY type exchange interaction under chemical pressure. The mechanism for this evolution is discussed in terms of the phase diagram proposed in the theoretical study [Wong et al., Phys. Rev. B 88, 144402, (2013)].