the substrate 11 is nonmetallic such as glass the seed layer 12 has a thickness in the range of approximately 1 to 50 nm and is one of the materials such as ta crti nial or rual which are useful as seed materials for promoting the growth of subsequently deposited layers in certain preferred crystalline orientations a pre seed layer not shown may also be used between the glass substrate 11 and the seed layer 12 the underlayer 13 is deposited onto the seed layer if present or otherwise directly onto the substrate 11 and is a nonmagnetic material such as chromium or a chromium alloy such as crv or crti the underlayer 13 has a thickness in the range of 5 to 100 nm with a typical value being approximately 10 nm the afc magnetic layer 20 is made up of two ferromagnetic films 22 24 separated by a nonferromagnetic spacer film 26 the nonferromagnetic spacer film 26 thickness and composition are chosen so that the magnetic moments 32 34 of adjacent films 22 24 respectively are af coupled through the nonferromagnetic spacer film 26 and are antiparallel in zero applied field the two af coupled films 22 24 of layer 20 have magnetic moments that are.