thick with 100 angstroms being preferred shown on chromium layer 24 is buffer layer 26 it is an alloy whose composition is between about 70 and 93 atomic percent cobalt between about 5 and 25 atomic percent chromium and between about 2 and 10 atomic percent tantalum with cobalt 82 chromium 14 and tantalum 4 being preferred its thickness is between about 10 and 100 angstroms with 20 angstroms being preferred on buffer layer 26 is magnetically hard layer 25 it is an alloy whose composition is between about 50 and 93 atomic percent cobalt between about 5 and 25 atomic percent chromium and between about 2 and 50 atomic percent platinum with cobalt 78 6 chromium 5 2 and platinum 16 2 being preferred its thickness is between about 100 and 600 angstroms with 400 angstroms being preferred this is the same as the first embodiment except that a layer of tantalum not shown has been inserted between substrate 13 and seed layer 24 it has a thickness between about 10 and 100 angstroms with 50 angstroms being preferred referring again to fig2 we show a structure that is similar to that of the first embodiment except that seed layer 24 is an alloy of chromium and titanium it is between about 20 and 150 angstroms thick with 100 angstroms being preferred its composition is between about 80 and 95 atomic percent chromium and between about 5 and 20 atomic percent titanium with cr 90 ti 10 being preferred this is the same as the third embodiment except that a layer of tantalum not shown has been inserted between substrate 13 and seed layer 24 it.