Nuclear magnetic resonance of51V (I=7/2) in lanthanide vanadates: I. The paramagnetic shifts

Abstract
Nuclear magnetic resonance of 51V (I=7/2) has been studied at temperatures down to 1.5K in single crystals of lanthanide vanadates LnVO4 where Ln3+ ranges from Pr3+, 4f2 to Yb3+, 4f13. The crystals are tetragonal, four molecules per unit cell, but all V5+ sites and all Ln3+ sites are magnetically equivalent. Measurements are made with applied fields parallel and perpendicular to the tetragonal axis, and fitted to the spin-Hamiltonian H=- gamma //h(cross)BzIz- gamma perpendicular to h(cross)(BxIx+ByIy)+P(Iz2-1/3I(I+1)). Values for the paramagnetic shifts are used to deduce the local fields at both the V5+ and Ln3+ sites. These fields are compared with the dipolar values, from which the magnitude of the transferred hyperfine interaction at the V5+ sites is deduced, together with estimates of the exchange interaction between the Ln3+ ions. The nuclear electric quadrupole interaction for 51V is discussed in paper II, and measurements in the antiferromagnetic phases of GdVO4 and DyVO4 in paper III.

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