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  Anand, V.K.; Opherden, L.; Xu, J.; Adroja, D.T.; Islam, A.T.M.N.; Herrmannsdoerfer, T.; Hornung, J.; Schoenemann, R.; Uhlarz, M.; Walker, H.C.; Casati, N.; Lake, B.: Physical properties of the candidate quantum spin-ice system Pr₂Hf₂O₇. Physical Review B 94 (2016), p. 144415/1-11

10.1103/PhysRevB.94.144415
Open Access Version

Abstract:
Physical properties of a pyrohafnate compound Pr2Hf2O7 have been investigated by ac magnetic susceptibility χac(T), dc magnetic susceptibility χ(T), isothermal magnetization M(H), and heat-capacity Cp(T) measurements on polycrystalline as well as single-crystal samples combined with high-resolution synchrotron x-ray diffraction (XRD) for structural characterization and inelastic neutron scattering (INS) to determine the crystal-field energy-level scheme and wave functions. Synchrotron XRD data confirm the ordered cubic pyrochlore (Fd¯3m) structure without any noticeable site mixing or oxygen deficiency. No clear evidence of long-range magnetic ordering is observed down to 90 mK, however the χac(T) evinces slow spin dynamics revealed by a frequency dependent broad peak associated with spin freezing. The INS data reveal the expected five well-defined magnetic excitations due to crystal-field splitting of the J=4 ground-state multiplet of the Pr3+. The crystal-field parameters and ground-state wave function of Pr3+ have been determined. The Ising anisotropic nature of the magnetic ground state is inferred from the INS as well as χ(T) and M(H) data. Together these properties make Pr2Hf2O7 a candidate compound for quantum spin-ice behavior.