0.15 0.10 0.05 0 Paramagnetic Susceptibility ( GLYPH<s109> B /Co T) 300 200 100 0 Temperature (K) -0.02 -0.01 0 0.01 0.02 Magnetization ( GLYPH<s109> B /Co) -2 -1 0 1 2 Magnetic Field (T) -4 0 4 -2 -1 0 1 2 P$_{O2}$ =10 $^{3}$ Pa  20 K  300 K P$_{O2}$ =10 $^{2}$ Pa 10 K  300 K Zn$_{0.9}$Co$_{0.1}$O (a) (b) P$_{O2}$ =10 $^{3}$ Pa P$_{O2}$ =10 $^{2}$ Pa Zn$_{0.9}$Co$_{0.1}$O FIG. 1: (Color online) Magnetic properties of Zn$_{0}$$_{.}$$_{9}$Co$_{0}$$_{.}$$_{1}$O thin films measured by a SQUID mag- netometer. (a) Magnetic-field ( H ) dependence of the magnetization. The H -linear components deduced from high H data have been subtracted. The inset shows raw data containing the diamag- netic signals from the substrates. (b) Temperature ( T ) dependence of the paramagnetic component of the magnetization represented in the form of magnetic susceptibility, where the T -independent component deduced from high- T data have been subtracted. 16