Structural and Magnetic study of Al 3+ doped Ni 0.75 Zn 0.25 Fe 2-x Al x O 4 nanoferrites
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Structural and Magnetic study of Al3+ doped Ni0.75Zn0.25Fe2-xAlxO4 nanoferrites L. Wang, B. K. Rai, and S. R. Mishra Department of Physics, The University of Memphis, Memphis, TN 38152 Abstract Nanostructured Al3+ doped Ni0.75Zn0.25Fe2-xAlxO4 (x = 0.0,0.2,0.4,0.6,0.8, and 1.0) ferrites were synthesized via wet chemical method. X-ray diffraction, transmission electron microscopy, and magnetization measurements have been used to investigate the structural and magnetic properties of spinel ferrites calcined at 950 oC .With the doping of Al3+, the particle size of Ni0.75Zn0.25Fe2-xAlxO4 first increased to 47 nm at x = 0.4 and then decreased down to 37 nm at x = 1. Saturation magnetization decreased linearly with Al3+ due to magnetic dilution. The coercive field showed an inverse dependence on the particle size of ferrites. Introduction Due to their various technological applications, NiZn-ferrites have attracted recently considerable research interest [1]. The performance of these materials in the bulk form with grain dimensions in micrometer scales is limited to a few megahertz frequency due to their higher electrical conductivity and domain wall resonance [2,3]. However, the recent technological advances in electronics industry demand compact ferrite cores to work at higher frequencies [4]. One way to circumvent this problem is by synthesizing the ferrite particles in nanometric scales before compacting them for sintering. When the size of the magnetic particle is smaller than the critical size for multidomain formation, the particle is in a single domain state. Domain wall resonance is avoided, and the material can work at higher frequencies. In addition, it is known that magnetic properties of ferrites are sensitive to preparation technique and their microstructures [5]. The dielectric and magnetic properties of such ferrites depend strongly on preparation methodology and distribution of cations at the tetrahedral (A) and octahedral (B) sites in the lattice [6,7,8,9]. Thus any alteration to the cation distribution in ferrites can alter their electrical and magnetic properties. These atomic level changes in ferrites can be engineered via doping desired level of magnetic or non-magnetic atoms for cations, which in turn affect the crystal structure and eventually influence Fe(A)-O-Fe(B) interactions. Therefore, the selection of appropriate additives is key to obtaining high performance ferrites. In this work, we present the results of systematic doping of non-magnetic Al3+ content on the magnetic properties of Ni0.75Zn0.25Fe2-xAlxO4 ferrite synthesized via wet chemical method. Aluminum ions have been proven to have substantial influence on M-Ferrites (M=Al, Co, Mg, Li, etc.), especially increasing resistivity and reducing eddy current losses [10,11,12]. The doping of naon-magnetic Al3+ in NiZn-Ferrite not only brings grain refinement but also alters magnetic properties to a great extent. Experimental
One pot method was used to synthesis Ni0.75Zn0.25Fe2-xAlxO4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1). Ni(NO3)2. 9H2O, Zn(NO3)2 .9
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