Magnetic domain control of thick Fe-M(Zr,Ta)-N films for digital VCR metal in gap heads

Magnetic domain structures of thick and small area (45×45×5 μm3) Fe-M(Zr or Ta)-N films were observed by a scanning Kerr-effect microscope (SKEM). The important factors in controlling the magnetic domains are the magnetostriction and the uniaxial anisotropy. By changing the N content in bcc Fe and the Ar pressure during sputtering, the saturation magnetostriction constant λs and the anisotropy field Hk were controlled in the range of 3×10−6–6×10−6 and 10–130 A/m, respectively. Clear and consecutive changes in the domain structures were observed by varying the film’s λs, Hk, and stress σ, and the observed structures agree qualitatively with the structures predicted by theoretical calculations. The wall structure where Bloch-like rotations and the Neel-like rotations are combined was observed by SKEM. The metal in gap heads using different λs and Hk films were fabricated and the output at 20 MHz was measured. A lower Hk is not necessarily better for obtaining a higher output in high-frequency ranges. The head output depends on the film’s magnetic domain structure, and the structure can be controlled by changing the λs and Hk.