Abstract: A magnetic recording medium wherein a magnetic metal film has been formed on one surface of a non-magnetic substrate, and a back coat resulting from a non-magnetic pigment dispersed among a binder has been formed on the other, or reverse to the side upon which the magnetic film has been formed, characterized by that each of the chloride and sulfate ion contents of the back coat, according to the analysis by ion chromatography of its pure water extract, is not more than 5 ppm, and that the binder acting as a constituent of the back coat contains at least polycarbonate urethane.

Abstract: A perpendicular magnetic recording medium having a magnetic layer comprised of a metal magnetic thin film on a nonmagnetic support. The half-value width of the switching field distribution obtained from a remanent magnetization curve in the intrinsic easy direction of magnetization (axis of easy magnetization from which shape magnetic anistrophy is removed) of the magnetic layer is no more than 40 kA/m.Rectangular wave signals are recorded or reproduced on or from a Co--O type perpendicular magnetic recording medium with a direction .theta..sub.E of the axis of easy magnetization tilted in a range of 10.degree. to 45.degree. from the direction perpendicular to the plane of the film of the magnetic layer using a ring type magnetic head with a gap length Lg of not more than 0.18 .mu.m.