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A new type of high‐resistive soft magnetic amorphous film possessing superior properties such as high resistivity (ρ), high‐saturation induction (Bs), and high permeability (μ) in the high‐frequency range prepared by cosputtering Co0.40Fe0.40B0.20‐SiO2 was obtained. These films which have Bs higher than 8 kG in the range less than ∼55% of Si‐O volume fraction, consist of a two‐phase structure of amorphous magnetic metal particles (∼50 A) scattered in the amorphous nonmagnetic Si‐O region. ρ increases exponentially with the increase of Si‐O volume, with diminishing eddy current loss in the very high‐frequency range. Some of these films (Bs∼12 kG, Hc∼0.3 Oe, ρ∼500 μΩ cm), in fact, have a superior permeability compared with sputtered sendust films and regular amorphous films used as high‐density recording head cores in the high‐frequency range over 10 MHz.

A new type of ferromagnetic amorphous alloy with a two‐phase structure was found in cosputtered Fe‐B‐N films. The microstructure was identified to be composed of two amorphous phases with about 50 A or less in size; one is a ferromagnetic amorphous phase of Fe‐B‐N alloy and the other is a nonmagnetic and high resistive amorphous phase of boron nitride. The homogeneous mixture of these two phases in the films resulted in unique features for magnetic and electrical properties. In comparison to sputtered Fe‐B films, the Fe‐B‐N films exhibit higher saturation magnetizations and the electrical resistivity is about 3–103 times higher. The compositional dependence of Curie and crystallization temperatures also differs from those of the sputtered amorphous Fe‐B films. Furthermore, the corrosion resistance of the films is improved in the presence of nitrogen.

A new type of high‐resistivity soft magnetic amorphous alloy film with a very fine two‐phase heterostructure was found in cosputtered Fe‐B‐C films. These amorphous films are found to have a number of superior properties in the high‐frequency range (over∼10 MHz) over not only regular amorphous films, but also sendust film cores, which have already been applied to high‐density recording media having high coercivity. They were found to exhibit unique isotropic soft magnetic B‐H curves with high Bs (∼15 000 G), low Hc (∼0.3 Oe), and high ρ (∼400 μΩ cm), and the reduced magnetization versus reduced temperature curve was almost the same as the j=∞ curve of the Brillouin function. A very high permeability with less core loss, especially in the high‐frequency range, was also experimentally observed in those amorphous films.

A novel type of shielded magnetoresistive (MR) head with a 5- mu m tack width is discussed. Its primary feature is the suppression of Barkhausen noise. The head also has low crosstalk and stable output level, which enables a rigid disk drive to achieve high track densities above 2500 tracks per inch. >

The effect of magnetic fields on the magnetic domain structure in thin iron films (∼200 A) has been studied in situ by Lorentz microscopy in an electrostatic transmission electron microscope (TEM). The electrostatic instrument provides a specimen region free of magnetic fields. A special solenoid was placed in the specimen region, coaxial with the optic axis. By tilting the specimen holder a known in‐plane component of the field could be applied to the specimen. Studies were made with the in‐plane field applied parallel to and perpendicular to the domain walls.

The Lorentz and Foucault methods have been used to study twisted domains in thin (∼200 A) iron films (made by evaporation) in an electrostatic transmission electron microscope (TEM). Twisted domains have been observed to occur spontaneously, as well as during and after the application of an in‐plane magnetic field. We have found that twisted domains consist of alternate sections separated by roughly 90° domain walls. Between these sections and the surrounding domain the wall is alternately 90° and 180°. The ripple structure in the micrographs provides further evidence as to the directions of magnetization. When Blochline‐crosstie pairs are present, they occur on the 180° walls but not on the 90° walls.