磁気ヘッド用磁性材料としての6%Vパーマロイの磁気的および機械的性質

Abstract

The suitability of a 6%V permalloy for magnetic head materials used in a digital tape recording equipment of an electronic computer was investigated in comparison with high permeability permalloys commonly used, e.g., 4%Mo-5%Cu permalloy and 4%Mo permalloy.Measurements of dc magnetic properties, ac magnetic permeabilities at H=0.4 A/m (frequency range 1-300 kHz) and its stress-sensitivity, e.g., the change in effective permeability caused by application of the compressive stress 1 MPa perpendicular to the sheet surfaces, were carried out for these permalloys 0.1, 0.05 and 0.025 mm in sheet thickness, subjected to various heat treatments. Wear tests were carried out by rubbing the test specimens of these permalloys against a γ-Fe2O3 magnetic tape at the running speed of 3 m/s. The saturation magnetostriction, the electrical resistivity and the mechanical hardness were also measured.Results obtained are summarized as follows:(1) The V permalloy examined has a better ac magnetic permeability at a high frequency range as well as a better dc magnetic properties than the compared alloys, and in particular its magnetic properties at low annealing temperatures below 1173 K are characteristically superior to those of the familiar high permeability permalloys.(2) The stress-sensitivity in the magnetic properties of the V permalloy is much smaller than that of the compared alloys at any examined annealing temperatures and exciting frequencies, so that values of permeabilities under the compressive stress remain very high.(3) Thin oxide films are formed on the contact surface of the V permalloy specimen during rubbing against the γ-Fe2O3 magnetic tape at high speed, and this formation brings about the wear-resistance property superior to that of the compared alloys.(4) The V permalloy has the same degree of mechanical hardness as other technical soft permalloys, and hence has a good workability.(5) From these results, the 6%V permalloy is an excellent and favourable alloy as a magnetic head material.