Néel Temperatures of Chromium-Vanadium Alloys from NMR Measurements

The antiferromagnetic transition temperature of chromium-rich V-Cr alloys has been investigated by means of the extinction of the 51V and 53Cr NMR signals at the transition temperature in these alloys. Measurements on both natural and isotopically enriched 53Cr chromium yield TN=39.0±0.5°C, in excellent agreement with neutron diffraction results. TN decreases roughly linearly with V content, falling below 4.2°K at 3.4% V. In all cases, the resonance intensity follows the empirical behavior, I=I0 tanh K(1-TN/T), where K ≈ 15. At temperatures well above TN, the linewidth and second moment of the 53Cr resonance are appreciably larger than the calculated values based solely on nuclear dipolar broadening. These results might be attributed to the persistence of a very small electronic moment in the paramagnetic state.