Magnetostriction of Co-base amorphous alloys and high frequency permeability in their sputtered thin films (invited)

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Abstract
For new magnetic materials with high permeability at MHz frequencies as well as high magnetic induction, magnetic properties of Co-base amorphous alloys produced by a sputtering technique were investigated. Small magnetostrictions, important for this purpose, were found in the Co-Nb-Ti system and Co-(Fe, Mn)-Nb system. The dipole-type model explained the concentration dependence of magnetostriction. In order to increase permeability at high frequencies by reducing eddy current losses, these amorphous alloys were made into thin film form. It was found that dc coercivity for the single film (about 3 μm thick) of Co80 Nb20 with negative magnetostriction was larger than that for Co80Ti20 with positive magnetostriction, while the layered films of Co80Nb20 separated by a SiO2 insulator showed small coercivities. Permeabilities of about 4×103 at 1 MHz and 1×103 at 10 MHz were obtained in the Co80Nb20/SiO2 and Co80Ti20/SiO2 layered films.