Herein, a discussion of the effect of deposition temperature on the magnetic behavior of Ni0.5Zn0.5Fe2O4 thin films. The thin films were grown by r.f. sputtering technique on (10 0) MgO single-crystal substrates at deposition temperatures ranging between 400 and 800 1C. The grain boundary microstructure was analyzed via atomic force microscopy (AFM). AFM images show that grain size (f_70–112 nm) increases with increasing deposition temperature, according to a diffusion growth model. From magneto-optical Kerr effect (MOKE) measurements at room temperature, coercive fields, Hc, between 37and 131 Oe were measured. The coercive field, Hc, as a function of grain size, reaches a maximum value of 131 Oe for f _93 nm, while the relative saturation magnetization exhibits a minimum value at this grain size. The behaviors observed were interpreted as the existence of a critical size for the transition from single- to multi-domain regime. The saturation magnetization (21emu/ goMso60 emu/g) was employed to quantify the critical magnetic intergranular correlation length (LcE166 nm), where a single-grain to coupled-grain behavior transition occurs. Experimental hysteresis loops were fitted by the Jiles–Atherton model (JAM). The value of the k-parameter of the JAM fitted by means of this model (k/mo_50 Am2) was correlated to the domain size from the behavior of k, we observed a maximum in the density of defects for the sample with f_93 nm.
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