Synthesis and magnetic properties of FeNi3/Al2O3 core-shell nanocomposites

In this study, FeNi3/Al2O3 core-shell nanocomposites, where individual FeNi3 nanoparticles were coated with a thin layer of alumina, were fabricated by a modified sol-gel method. Several physical characterizations were performed on the samples of FeNi3/ Al2O3 nanocomposites with different thickness of Al2O3 shell. The encapsulation of FeNi3 nanoparticles with alumina stops FeNi3 agglomeration during heat treatment, and prevents interaction among the closely spaced magnetic FeNi3 nanoparticles. The Al2O3 insulating shell improves the soft magnetic properties of FeNi3. The study of the complex permeability of the samples shows that the real part mu' of the permeability of the sample with Al molar content of 20% (Al/(Fe+ Ni)) is as high as 12, and independent of frequency up to at least 1 GHz. The tunneling magnetoresistance arising from the presence of the Al2O3 shell have also been studied.