Chapter 7 - Horizontal Biasing Techniques

Abstract

Horizontal biasing is necessary in all magneto-resistive heads (MRHs) so that the single-domain magnetization state of the magneto-resistive element (MRE) or sensor film can be stable against all reasonable perturbations. These perturbations include external magnetic fields and thermal and mechanical stresses. The primary function of the horizontal bias is to keep the MRE in the single-domain state. When the horizontal bias is not adequate to keep the MRE single domain, domain wall jumps change the demagnetizing field in the MRE. This changes the magnetization versus current angle and changes the variable resistance versus field characteristic curve. Many of the techniques used for producing vertical bias are proposed for horizontal bias. Again, the field is replete with novelty and ingenuity. The permanent magnetic (PM) film arrangement is used for applying both vertical and horizontal bias fields by merely setting the PM film's magnetization at an oblique angle. This chapter concludes with some horizontal biasing arrangements, which are not merely simple adaptations of vertical bias methods and include: conductor overcoat, exchange tabs, hard films, and closed flux.