NMR of YbVO4 thermally detected by nuclear orientation

Full text: Rare earth vanadates have interesting low temperature magnetic properties because the nuclear and electronic wavefunctions become mixed, leading to a variety of interesting physical effects, such as ground state enhanced nuclear magnetism, and quadrupolar induced re-orientation in intermediate level excited states. As the electronic ordering temperatures of selected rare earth vanadates fall to very low temperatures (sub 1K) one may anticipate, for concentrated rare earth nuclear spin species, complex collectively coupled electron-nuclear systems through the strong magnetic hyperfine interaction. These effects are conveniently investigated through NMR. To this end we have recently successfully employed NMR Thermally Detected by Nuclear Orientation (NMR-TDNO) to investigate naturally abundant (14.31%) 171Yb (I=1/2) in the single crystal antiferromagnetic insulator YbVO4, (Neel temperature ∼ 93mK), at lattice temperatures of order 40mK. In this paper we present further NMR-TDNO results for the 171Yb isotope. NMR-TDNO is observed by perturbations on gamma anisotropy from 169,175Yb impurity nuclei obtained by in situ neutron irradiation of the YbVO4 single crystals and also for a non-irradiated single crystal YbVO4 using external gamma ray thermometry. Other, as yet unidentified, absorptions of rf energy in YbVO4 are also discussed