Professor John Gregg

Abstract:

For pt.I see ibid., vol.15, p.5275 (1982). Nuclear magnetic resonance of 51V (I=7/2) in the tetragonal zircon structure LnVO4 of the lanthanide vanadates is used to measure the nuclear electric quadrupole splitting term P(Iz2- 1/3I(I+1)). Values of mod P/h mod have been determined for all members of the series from Pr3+ to Lu3+ except Pm3+, but including Y3+. The values are found to vary smoothly with the ratio c0/a0, where c0, a 0 are dimensions of the unit crystal cell. A point-charge calculation of the electric field gradient Vzz of the lattice gives general agreement with the experimental result that mod P/h mod diminishes as c 0/a0 increases. From the value Q=-0.052(10) of Childs (1967), the Sternheimer parameter gamma infinity is found to be -12(3) on the basis that P is positive.

Abstract:

Nuclear magnetic resonance measurements of 50V and 51V in the weak paramagnet SmVO4 at low temperatures have been fitted to the spin Hamiltonian. H=- gamma /sub ///h(cross)B zIz- gamma perpendicular toh(cross)(B xIx+ByIy)+P(Iz2-1/3I(I+1)). The measured ratio of the quadrupole splittings gives an improved value for the ratio of the nuclear electric quadrupole moments mod 50Q/51Q mod =4.019(4).