Theoretical studies of {63}^Cu Knight shifts of the normal state of YBa_2Cu_3O_7

Abstract

The 63 Cu Knight shifts and g factors for the normal state of YBa 2 Cu 3 O 7 in tetragonal phase are theoretically studied in a uniform way from the high (fourth-) order perturbation formulas of these parameters for a 3d 9 ion under tetragonally elongated octahedra. The calculations are quantitatively correlated with the local structure of the Cu 2+ (2) site in YBa 2 Cu 3 O 7 . The theoretical results show good agreement with the observed values, and the improvements are achieved by adopting fewer adjustable parameters as compared to the previous works. It is found that the significant anisotropy of the Knight shifts is mainly attributed to the anisotropy of the g factors due to the orbital interactions.