Title: Muon spin relaxation and inelastic neutron scattering investigations of all-in/all-out antiferromagnet Nd2Hf2O7,
Abstract: Nd2Hf2O7, belonging to the family of geometrically frustrated cubic rare
earth pyrochlore oxides, was recently identified to order antiferromagnetically
below T_N = 0.55 K with an all-in/all-out arrangement of Nd3+ moments, however
with a much reduced ordered state moment. Herein we investigate the spin
dynamics and crystal field states of Nd2Hf2O7 using muon spin relaxation (muSR)
and inelastic neutron scattering (INS) measurements. Our muSR study confirms
the long range magnetic ordering and shows evidence for coexisting persistent
dynamic spin fluctuations deep inside the ordered state down to 42 mK. The INS
data show the crytal electric field (CEF) excitations due to the transitions
both within the ground state multiplet and to the first excited state
multiplet. The INS data are analyzed by a model based on CEF and crystal field
states are determined. Strong Ising-type anisotropy is inferred from the ground
state wavefunction. The CEF parameters indicate the CEF-split Kramers doublet
ground state of Nd3+ to be consistent with the dipolar-octupolar character.