SUSCEPTIBILITY AND Y-89 NUCLEAR-MAGNETIC-RESONANCE IN Y1-XCAXVO3

Temperature-dependent (10-300 K) field-cooled (FC) and zero-field-cool ed (ZFC) susceptibilities, and Y-89 NMR spectra and relaxation in Y1-x CaxVO3 with 0 less than or equal to x less than or equal to 0.9 are re ported. In the paramagnetic phase (PA) of YVO3 and for T greater than or equal to 120 K the susceptibility chi is of antiferromagnetic (AF) type, with no field dependence. Around the Neel temperature T-N((1))=1 13+/-1 K a field-dependent ferromagnetic behavior is observed under FC condition. Below T-N((2))similar or equal to 77 K (AF phase with AF i nterplane coupling) strong difference is present between FC and ZFC ch i's. For T-->T-N((1)+) the Y-89 NMR line shows marked broadening and n o measurable shift, consistent with a dominant dipolar contribution in the nucleus-electrons interaction. The Y-89 relaxation rate T-1(-1), related to the correlated spin dynamics of V3+ S(t), seems to indicate that the interplane ferromagnetic symmetry of the spin fluctuations i s quenched in strong fields. The peculiar findings for chi and T-1 cou ld result from a field-dependent weak ferromagnetism of Dzyaloshinsky- Moriya character. In Y1-xCaxVO3, chi and T-1(-1) decrease on increasin g x, still preserving the qualitative behavior as for x=0. For x simil ar or equal to 0.6 (Ca concentration which drives the transition to th e metallic phase) the marks of the PA-AF transition are practically su ppressed and behaviors characteristic of correlated metals are observe d. (C) 1996 American Institute of Physics.