Patent ID: 6790522
Filing Date: 2004-09-14
Classification: G11B

Abstract:
A magnetic recording medium comprising a support having provided thereon a magnetic layer containing a barium ferrite powder dispersed in a binder, wherein the barium ferrite powder has SBET of 40-80 m2/g, wherein the barium ferrite powder is subjected to surface treatment with oxides or hydroxide of Si, Al or P, silane coupling agents, or titanium coupling agent in an amount of from 0.1 to 10 weight %, and is washed with water or weak acid after the surface treatment, the binder has a â€”SO3M group wherein M represents a hydrogen atom or an alkali metal salt group and the concentration of Ba of the extract obtained by the following condition is 20 ppm or less per m2 of the magnetic recording medium:condition: 0.05 m2 of the magnetic recording medium is arbitrarily cut out and put in a 200 ml beaker with 100 ml of distilled water, the beaker is covered with a watch glass and retained in a constant temperature bath at 75Â° C. for 3 hours.