Study on the Origin of the Large Field Induced Magnetic Anisotropy of Nano-granular Soft Magnetic films and Its Applications

点击翻译按钮获取中文摘要

Soft magnetic metal-insulator nano-granular thin films such as (Fe, Co, Ni metals and their alloys)-(Al, Mg, RE oxides, nitrides and fluorides) are considered as the thin film-type high frequency magnetic inductive core materials, because of their high electrical resistivity (ρ), magnetic moments (Bs) and magnetic anisotropy field (Hk). We have found that the Co based films containing more than 10 at. % Pd exhibit huge Hk more than 200 Oe in keeping large ρ and Bs. The Hk is controllable in magnitude as well as in its uniaxial direction by adjusting of field-annealing conditions. A large Hk brings remarkable increase in the resonance frequency (fr) up to GHz region. In this project, we investigate the dependence of magnetic anisotropy (Ku) on field-annealing condition and composition for nano-granular soft magnetic films, and examine the origin of a large Ku of nano-granular Co-Pd based films from the structural experiments and discuss the applications of these films. Films were prepar … More ed by rf reactive magnetron sputtering with Ar+O_2 gases. Magnetic measurements were conducted on both a vibrating sample magnetometer and a torque magnetometer. The features of the Ku for metal-insulator type nano-granular soft magnetic films can be summarized into four things; 1) extraordinary large magnitude of Ku, as large as 1.5x 10^5 erg/cc is found in Co-Pd-Si-O films, 2) Ku of the films is attributed to a magnetically field induced anisotropy, 3) unique materials dependence of Ku is found as Co-Pd based>Co based>Fe based films, and 4) anomalous compositional dependence of Ku in (FeCo)-AI-O films cannot be explained in terms of the atom pair ordering. Structural investigations by HREM and SAXS have revealed a model to explain the Ku of Co-Pd-Si-O films. A large Ku of Co-Si-Pd-O films is attributed to a realignment of atoms at interfaces between granules and between granule and matrix, resulting in a strong anisotropy due to Co-Pd surrounded by a low symmetrical atomic environment. A crystal magnetic anisotropy of granule metals may also be related to the magnitude of Ku in the films. These soft magnetic thin films will be a strong candidate for magnetic core materials of inductor and transformer and so on at a few GHz range. And their large permeability near fr suggests that these films are a suitable for the electromagnetic noise suppression materials at GHz band. Less