ORBITAL AND SPIN SUSCEPTIBILITIES OF THE PLANE COPPER SITES IN YBA2CU3OX SYSTEM

The tensor components of the magnetic susceptibility (chi) and the Knight shift (K) at the plane Cu(2) sites have been precisely measured in YBa2Cu3Ox with x=6.98, 6.48 and 6.0. Using the temperature dependent chi and K observed in YBa2Cu3O6.48, we have carried out the analysis of K-chi diagram to make a separation of the observed susceptibility into orbital and spin contributions. Assuming the orbital contribution from the Cu(2) ions is independent of x for 6.0 less-than-or-equal-to x less-than-or-equal-to 7.0, we have obtained the x dependent spin susceptibility of the Cu(2) ions. The obtained spin susceptibility is discussed in comparison with the theoretical predictions of the Heisenberg model, the Stoner model and a band structure calculation. A complete set of the parameter values used in the crystal field model of a Cu2+ ion (the crystal field splittings, the orbital reduction factor, the spin-orbit coupling and the g-factors) has been determined from the K-chi analysis.