We report pulsed magnetization and 23N a NMR studies of a quantum phase transition and its associated spin dynamics in a 3d1 system, using the alkali-metal peroxychromate K2NaCrO8. This is an example of a Cr5+-based S=1/2 and I∼0 material with a clearly defined TN=1.7 K in zero applied field (H). Its magnetization (M) shows a nonlinear increase with H, in contrast to a simple three-dimensional antiferromagnet, and saturates at HC=7.4 T. This easily accessible HC allows for a detailed study by 23N a NMR of the magnetic-field-induced quantum phase transition from the antiferromagnetically ordered to a ferromagnetically polarized phase. The critical exponent of M (T) ∼ (1-T/ TN)β is 0.44±0.05 at H=5 T but shows a definitive increase to 0.53±0.05 at 6.8 T, close to HC. This suggests that while the magnetic behavior of K 2NaCrO8 is largely describable by a mean-field theory, the field dependence of β remains unexplained.
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - 2008 Dec 1|