Study on the origin of induced magnetic anisotropy of metal-insulator nano-granular soft-magnetic film by small-angle X-ray and neutron scattering

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For achieving high density and fast electronic devices, soft magnetic materials with high-magnetic permeability at the GHz frequency regions are required. Nano-granular soft-magnetic films are one of the promising candidates because of their high saturation magnetization, large resistivity and large induced magnetic anisotropy field, Hk, that sometimes exceed 200 Oe. Except large Hk, the origin of the properties is attribute to the microstructure which consists of almost pure Co and Si-O base amorphous matrix. Elk also shows weak dependence of the average particle size, however, no microstructural anisotropy has been found yet. For full understanding of the origin of anisotropy, it is needed to know the magnetization process in the field smaller than Hk. For this purpose, we use small-angle neutron scattering (SANS). Our findings are follows;1. Intensity maximum in SANS appears parallel to the major axis of magnetization. This indicates the existence of minor contribution of magnetizat … More ion which lies perpendicular direction to the major magnetization axis.2. By applying magnetic field perpendicular to easy axis, the intensity maximum rotate continuously to the external field, indicating the minor contribution also rotate together with major component of magnetization.3. The size of the magnetic domain of minor component is changed by the external field. Larger in the small field and smaller in the field close to the Bk. Latter ease, it is about 10 nm which is still larger than the particle size (〜3nm). Magnetic domain size of the major component is larger than a few thousand nm that is the maximum size of our SANS measurements. Therefore, it indicates the existence of hierarchical structure in the magnetic domain.Such of hierarchical structure in the magnetic domain has never reported in the soft-magnetic materials. Hence it can be a key factor for showing large Bk. For confirming it, we are now conducting further experiments using stronger neutron source which starts from Dec. 2008. Less