Magnetic Ordering in the Spin-Ice Candidate Ho${}_2$Ru${}_2$O${}_7$

Abstract

Neutron scattering measurements on the spin-ice candidate material Ho${}_2$Ru${}_2$O${}_7$ have revealed two magnetic transitions at T $\sim$ 95 K and T $\sim$ 1.4 K to long-range ordered states involving the Ru and Ho sublattices, respectively. Between these transitions, the Ho${}^{3+}$ moments form short-ranged ordered spin clusters. The internal field provided by the ordered S=1 Ru${}^{4+}$ moments disrupts the fragile spin-ice state and drives the Ho${}^{3+}$ moments to order. We have directly measured a slight shift in the Ho${}^{3+}$ crystal field levels at 95 K from the Ru ordering.

4 pages, 5 figures, submitted to Phys. Rev. Letters