Determining the Hamiltonian of a New Quantum Spin Ice Material

Pr2Hf2O7 is a potential quantum spin ice compound. Compared to the classical spin ice ions Ho3+ and Dy3+, Pr3+ has weaker Ising anisotropy and significant XY terms leading to monopole fluctuations in the ground state. Pr2Hf2O7 does not develops long-range magnetic order down to the lowest measured temperature of 0.1K and while its excitations display pinch point like features at low energy transfers the they broaden significantly at higher energies suggesting enhanced dynamic correlations consistent with quantum spin ice. Here we wish to determine the Hamiltonian of Pr2Hf2O7 by using LET to measure the excitations in a magnetic field strong enough to suppress fluctuations and give rise to spin-wave excitations which can then be modelled and fitted to extract the couplings. This will provide a better understanding of Pr2Hf2O7 and a starting point from which to model the monopole dynamics.