Study on mechanism of soft magnetic properties for high-frequency application in Ni 75Fe 25-SiO 2 granular films

Abstract

Excellent soft magnetic properties have been achieved in a wide metal volume fraction (x) range for asdeposited (Ni 75Fe 25) x-(SiO 2) (1-x) granular films fabricated by magnetron sputtering. With x changes from 0.81 to 0.52, the films exhibit small coercivity (H c) not exceeding 5 Oe and high electrical resistivity ρ. The minimum H c value of 87.6 A m -1 was obtained for the sample of x = 0.81. At the frequency lower than 550 MHz, the real part μ′ of complex permeability keeps about 170 and the image part μ″ is less than 26. Especially, for the film with very low x (= 0.52), besides the low H c (∼3 Oe), very high ρ over 1.18 × 10 4 μΩ cm has been obtained. A combined study of TEM and XRD indicates that the samples consist of Ni 75Fe 25 particles uniformly embedded in insulating SiO 2 matrix. The excellent soft magnetic property is ascribed to the exchange coupling among magnetic particles due to the long exchange length of Ni 75Fe 25. The investigation of the Henkel plot evidences the existence of this intergranular interaction. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.