Revisiting Static and Dynamic Spin Ice Correlations in Ho2Ti2O7

TL;DR

This study investigates the static and dynamic spin correlations in Ho2Ti2O7 spin ice using neutron scattering, revealing temperature-dependent diffuse scattering patterns, a transition from dynamic to static correlations below 2 K, and field-sensitive chain correlations.

Contribution

It provides detailed neutron scattering analysis of Ho2Ti2O7, highlighting temperature and field effects on spin correlations and the transition from dynamic to static spin states.

Findings

Diffuse elastic scattering appears below ~17 K.

Well-defined zone boundary peaks develop below ~2 K.

Transition from dynamic to static correlations occurs below ~2 K.

Abstract

Elastic and inelastic neutron scattering studies have been carried out on the pyrochlore magnet Ho2Ti2O7. Measurements in zero applied magnetic field show that the disordered spin ice ground state of Ho2Ti2O7 is characterized by a pattern of rectangular diffuse elastic scattering within the [HHL] plane of reciprocal space, which closely resembles the zone boundary scattering seen in its sister compound Dy2Ti2O7. Well-defined peaks in the zone boundary scattering develop only within the spin ice ground state below ~ 2 K. In contrast, the overall diffuse scattering pattern evolves on a much higher temperature scale of ~ 17 K. The diffuse scattering at small wavevectors below [001] is found to vanish on going to Q=0, an explicit signature of expectations for dipolar spin ice. Very high energy-resolution inelastic measurements reveal that the spin ice ground state below ~ 2 K is also characterized by a transition from dynamic to static spin correlations on the time scale of 10^{-9} seconds. Measurements in a magnetic field applied along the [1${\bar1}$0] direction in zero-field cooled conditions show that the system can be broken up into orthogonal sets of polarized alpha chains along [1${\bar1}$0] and quasi-one-dimensional beta chains along [110]. Three dimensional correlations between beta chains are shown to be very sensitive to the precise alignment of the [1${\bar1}$0] externally applied magnetic field.