Co ions as that of the ferromagnetic hetero-epitaxial Zn$_{1}$$_{−}$$_{x}$Co$_{x}$O thin film [see Fig. 2(b)], which did not show a Curie-Weiss paramagnetic component. The results imply that although the Co ions substitute for the Zn sites, the Co ions become paramagnetic or ferromagnetic in Zn$_{1}$$_{−}$$_{x}$Co$_{x}$O depending on n and the crystallinity. Considering that Co 2 p XMCD reflects only the local electronic states of the Co ion, it is likely that the different magnetic responses of the Zn$_{1}$$_{−}$$_{x}$Co$_{x}$O films are originated from different nearest and next-nearest neighbor interaction with neighboring cations, defects, and/or carrier concentration. We shall discuss about the differences in the magnetic properties below. Let us quantitatively discuss the paramagnetic behavior of the Co ions by applying XMCD sum rules to the spectra [32, 33]. The H and T dependences of M$_{tot}$ have been fitted to the formula where C is the Curie constant and θ is the Weiss temperature. The second term M$_{s}$ in Eq. (1) is contributions from the ferromagnetic component. Results of the fit are shown in Figs. 3(b) and 4(b), indicating that Eq. (1) well reproduces both the H and T dependences of M$_{tot}$ . The fitted parameters are listed in Table I. It should be noted that the obtained M$_{s}$ ’s well agree with those deduced from the magnetization measurements as shown in Table I, providing experimental evidence that we have probed the intrinsic bulk magnetic properties of the Zn$_{1}$$_{−}$$_{x}$Co$_{x}$O thin films. In addition, the agreement suggests that magnetic moment of the substituted Co ions is predominant source of the ferromagnetic responses of the samples expected to be in the low n region. The C values estimated from the Curie-Weiss fit are close to that of the free Co 2+ ion with quenched orbital moment of ∼ 3.36 µ$_{B}$ K/T, except for the P$_{O2}$ =10 − 2 Pa thin film. The Weiss temperature θ of all the samples are negative, consistent with the report of antiferromagnetic interaction in paramagnetic Zn$_{1}$$_{−}$$_{x}$Co$_{x}$O thin films [18]. In order to see the effects of vacuum annealing on the electronic and magnetic properties of the Co ion, we have measured the Co 2 p XMCD spectra of the P$_{O2}$ =10 − 2 Pa film after vacuum annealing, too. Figure 5(a) shows the Co 2 p$_{3}$$_{/}$$_{2}$ XAS and XMCD spectra of the P$_{O2}$ =10 − 2 Pa film before and after the annealing. The line shapes of the XAS and XMCD spectra are almost identical before and after the annealing, indicating that the local elec- tronic structure of the Co ion remained unchanged by the annealing. However, the XMCD intensity of the annealed sample becomes about half of the value of the as-grown one. The 8 〈 M$_{tot}$ 〉 = CH T − θ + M$_{s}$, (1)