FILM SM-CO PERMANENT-MAGNETS FOR THE BIASING OF THIN PERMALLOY STRIPS

Highly textured Sm-Co-based permanent magnet films which exhibit in-pl ane anisotropy, with thicknesses ranging from 500 angstrom to several microns, have been synthesized on polycrystalline Al2O3 substrates. Th e textured Sm-Co-based films of the disordered TbCu7-type structure we re directly crystallized by sputter deposition onto heated substrates. Remanent inductions B(R) were almost-equal-to 8 kG, and the intrinsic coercivities, (i)H(c), ranged from 4-10 kOe. The crystallite grain si ze as a function of film thickness was determined. The use of these fi lms in small scale geometry devices was tested in a sandwich configura tion of strips of areal size 7 X 1 mm2. The Sm-Co films were used to b ias Ni81.5Fe18.5 permalloy films. The sandwich permanent magnet was ma gnetized across its width. The permalloy films were sputter synthesize d under conditions very similar to those of the permanent magnet films . Substrate biasing was not used for either the permanent magnet or th e permalloy strips. The permalloy films exhibited a well-defined easy axis along the length of the strip. Unbiased, the permalloy showed a m aximum magnetoresistance MR(max) of 3.0%. On biasing with a 25-mum-thi ck permanent magnet film with a spacer thickness of 25 mum, the longit udinal biasing field value at MR/MR(max) = 0.5 was more than a 100 Oe, indicating an average biasing field of the same value.