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ARTICLE IN PRESS
Journal of Magnetism and MagneticMaterials 321 (2009) 2792–2794

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Journal of Magnetism and Magnetic Materials
journal homepage: www.elsevier.com/locate/jmmm

Growth temperature dependence of the hysteretic behavior of Ni0.5Zn0.5Fe2O4 thin films
´ J. Prado a, M.E. Gomez a, P. Prieto a,Ã, A. Mendoza b
a b

Thin Film Group, Department of Physics, Center of Excellence for NovelMaterials—CENM, Universidad del Valle, A.A. 25360 Cali, Colombia ´ Magnetic Materials and Nanostructures Group, Department of Physics, Universidad Nacional de Colombia, carrera 45 No 26-85, Bogota, Colombia

a r t i c l e in f o
Article history: Received 11 December 2008 Received in revised form 30 March 2009 Available online 17 April 2009 PACS: 75.50.Gg 75.60.Àd 75.60.Ch Keywords: Ferimagnetics Domaineffect Magnetization curve Hysteresis Domain wall

a b s t r a c t
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 (1 0 0) MgO single-crystal substrates at deposition temperatures ranging between 400 and 800 1C. The grain boundary microstructure was analyzed via atomic forcemicroscopy (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 relativesaturation 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 (21 emu/ goMso60 emu/g) was employed to quantify the critical magnetic intergranular correlation length (LcE166 nm), where a single-grain to coupled-grain behaviortransition 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 A m2) 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. & 2009 Elsevier B.V. All rights reserved.

1. Introduction Growth of magnetically softferrite thin films is motivated by their potential applications [1,2]; particularly, the study of NiZn ferrites with spinel structure is of current theoretical and technological interest. The magnetic properties of soft magnetic materials can be understood by adequate theoretical models [3,4]. Given their low conductivity, NiZn ferrites are used for highfrequency applications. For optimumperformance at these high frequencies, their magnetic hysteresis should also be as narrow as possible; said property is related to domain wall motion, and several studies have been conducted on the domain structure of poly-crystalline NiZn ferrites, along with their relationship to average grain size [5,6]. Generally, the magnetic quality of ferrite films is also mainly dependent on the extrinsic...