Antiferromagnetic order in the pyrochlores R2 Ge2 O7 (R= Er, Yb) ANTIFERROMAGNETIC ORDER in the PYROCHLORES ... Z. L. DUN et al.

Elastic neutron scattering, ac susceptibility, and specific heat experiments on the pyrochlores Er2Ge2O7 and Yb2Ge2O7 show that both systems are antiferromagnetically ordered in the Γ5 manifold. The ground state is a ψ3 phase for the Er sample and a ψ2 or ψ3 phase for the Yb sample, which suggests "Order by Disorder" physics. Furthermore, we unify the various magnetic ground states of all known R2X2O7 (R=Er, Yb; X=Sn, Ti, Ge) compounds through the enlarged XY-type exchange interaction J± under chemical pressure. The mechanism for this evolution is discussed in terms of the phase diagram proposed in the theoretical study by Wong et al. [Phys. Rev. B 88, 144402 (2013)PRBMDO1098-012110.1103/PhysRevB.88.144402].