Large-capacity magnetic memory card and manufacturing method

A magnetic memory card having at least 40 tracks/cm comprised of a 20-80 .mu.m thick polycarbonate support having on the major part of at least one of its surfaces a magnetic recording medium containing Ba or Sr hexaferrite particles having an aspect ratio of between 1.5:1 and 3:1, a length of 0.1 to 0.3 .mu.m and a coercive field with a strength of over 5000 Oe, a binder formed by a cross-linked three dimensional polyurethane formed from a branched polyol having a mean molecular weight of less than 4,000 and containing at least 8% by weight OH groups and an isocyanate prepolymer containing at least three isocyanate groups, and at least one solid particulate lubricant present in an amount of less than 2 wt % based on the weight of magnetic particles, said solid particulate lubricant being tetrafluoroethylene polymer particles of which at least 99% have a size smaller than 3 .mu.m, said magnetic recording medium having no overcoat layer and having an information density of at least 50 kbits/cm.sup.2, wear corresponding to a loss of electric signal equal to or smaller than 5% for 2000 passes, an average peak-to-valley height of less than 10 nm, an abrasive characteristic of less than 600 .mu.m, and a scratch resistance of less than 1.5 .mu.m.