Spin Correlations in Ho${}_2$Ti${}_2$O${}_7$: a Dipolar Spin Ice System

Abstract

The pyrochlore material $\mathrm{H}{\mathrm{o}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$ has been suggested to show ``spin ice'' behaviour. We present neutron scattering and specific heat results that establish unambiguously that Ho${}_2$Ti${}_2$O${}_7$ exhibits spin ice correlations at low temperature. Diffuse magnetic neutron scattering from Ho${}_2$Ti${}_2$O${}_7$ is found to be quite well described by a near neighbour spin ice model and very accurately described by a dipolar spin ice model. The heat capacity is well accounted for by the sum of a dipolar spin ice contribution and an expected nuclear spin contribution, known to exist in other Ho${}^{3+}$ salts. These results settle the question of the nature of the low temperature spin correlations in $\mathrm{H}{\mathrm{o}}_2\mathrm{T}{\mathrm{i}}_2{\mathrm{O}}_7$ for which contradictory claims have been made.

1 Color POSTSCRIPT figures included. 1 BW POSTSCRIPT figure included Submitted to Physical Review Letters Contact: [email protected] This version corrects for an incomplete version accidentally submitted the first time