Growth mechanism and electron spin resonance studies of Zn1−xNixO/NiO two-phase nanocomposite

Two-phase nanocomposites comprised of Zn_1-xNi_xO/NiO (0.05 ≤ x ≤ 0.3) were grown by using sol-gel process with hydrated metal acetates as precursors. Thermal decomposition of the co-precipitated oxalate α-ZnNi(C₂O₄) yields wurtzite h.c.p. Zn_1-xNi_xO and f.c.c. NiO together. The X-band electron spin resonance spectra provide the signatures of anisotropic spin interactions with long-range magnetic ordering at 300 K. The temperature variation (120 K ≤ T ≤ 300 K) of the resonance field H_R(T) and line-width ΔH_PP(T) depicts a clear anomaly across 140 K associated with the blocking/freezing effects and the contribution of additional surface anisotropy (K_eff) present in the system. Both H_R(T) and ΔH_PP(T) follows the power-law variation δH_R = (ΔH_PP)ⁿ with n ≃ 2.13, as expected for partially oriented nanocrystallites.