Magnetic Excitation Spectrum of Two New Rare Earth Pyrochlores

The aim of the proposed experiment is to explore the magnetic behavior of the new rare earth Pyrochlores Pr2Hf2O7 and Nd2Hf2O7 by using CNCS to measure their magnetic scattering. Both compounds promise interesting new physics. Pr2Hf2O7 may realise the long-sought-after quantum spin ice state expected for Pr3+ on a Pyrochlore lattice. This compound shows complete absence of long-range magnetic order despite substantial spin correlations revealed by AC susceptibility which verify a spin liquid ground state. In contrast,Nd2Hf2O7 develops long-range magnetic order with an all-in-all-out magnetic structure revealing that the magnetic interactions are antiferromagnetic rather than ferromagnetic as found in spin ice. Here strong diffuse scattering is also expected due to the highly suppressed ordered moment.