Susceptibility and 89Y nuclear magnetic resonance in Y1− x Ca x VO3

Temperature-dependent (10–300 K) field-cooled (FC) and zero-field-cooled (ZFC) susceptibilities, and 89Y NMR spectra and relaxation in Y1−xCaxVO3 with 0≤x≤0.9 are reported. In the paramagnetic phase (PA) of YVO3 and for T≥120 K the susceptibility χ is of antiferromagnetic (AF) type, with no field dependence. Around the Neel temperature T(1)N=113±1 K a field-dependent ferromagnetic behavior is observed under FC condition. Below T(2)N≂77 K (AF phase with AF interplane coupling) strong difference is present between FC and ZFC χ’s. For T→T(1)+N the 89Y NMR line shows marked broadening and no measurable shift, consistent with a dominant dipolar contribution in the nucleus–electrons interaction. The 89Y relaxation rate T−11, related to the correlated spin dynamics of V3+ S(t), seems to indicate that the interplane ferromagnetic symmetry of the spin fluctuations is quenched in strong fields. The peculiar findings for χ and T1 could result from a field-dependent weak ferromagnetism of Dzyaloshinsky–Moriya character. In Y1−xCaxVO3, χ and T−11 decrease on increasing x, still preserving the qualitative behavior as for x=0. For x≂0.6 (Ca concentration which drives the transition to the metallic phase) the marks of the PA–AF transition are practically suppressed and behaviors characteristic of correlated metals are observed.