Isotropic films for curved data tracks in a cross-tie memory

Abstract

Use of a serrated NiFe strip as a data track for a cross-tie memory was introduced by Schwee et al. [AIP Conf. Proc. 29, 624 (1975)]. Use of an isotropic film instead of an anisotropic one in such a strip has two advantages: it confines the wall in the central portion of the strip, and it permits the use of curved data tracks. The isotropic film is deposited on a rotating substrate in the presence of a dc orienting field in order to eliminate angle of incidence effects. Serrated strips are etched from these films. The edges of the serration supply a local shape anisotropy. Cross-tie walls run parallel to the local easy axis. If the magneticaly induced easy axis of an isotropic film is skewed with respect to the edge of the strip, the wall eventually intersects the edge; this is avoided by the use of isotropic films. Equations for the magnitude of the anisotropy and the skew angle are presented. Curved isotropic film strips were fabricated; placement of a cross-tie wall all around the curve was achieved via a curved stripline deposited under the NiFe film. The cross-ties in an isotropic film are wider than in an anisotropic film, drive currents are lower, and the effective area for magneto-resistive sensing larger.