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Modulus Encapsulated Yoke Structure for Magnetic Recording

IP.com Disclosure Number: IPCOM000115924D
Original Publication Date: 1995-Jul-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Cain, W: AUTHOR [+5]

Abstract

An encapsulation structure for improving the magnetic recording head yoke stability is disclosed (1). Stress relaxation during annealing causes observable changes in the permalloy micro-magnetic state. The amount of stress relaxation (2) is highly sensitive to the shape of the permalloy film and the encapsulation material. It is possible to tailor the yoke shape for specific flux conduction directions. After permalloy films with negative magnetostrictive coefficient are annealed, the easy axis of bar-shape yokes remains in the transversal direction while those of ring-shape yokes and heart-shape yokes rotate such that the easy axis is normal to the film edge. Permalloy films encapsulated entirely in hardbaked photoresist are consistently most stable, as compared to other encapsulation structures involving alumina material.

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Modulus Encapsulated Yoke Structure for Magnetic Recording

      An encapsulation structure for improving the magnetic recording
head yoke stability is disclosed (1).  Stress relaxation during
annealing causes observable changes in the permalloy micro-magnetic
state.  The amount of stress relaxation (2) is highly sensitive to
the shape of the permalloy film and the encapsulation material.  It
is possible to tailor the yoke shape for specific flux conduction
directions.  After permalloy films with negative magnetostrictive
coefficient  are annealed, the easy axis of bar-shape yokes remains
in the transversal direction while those of ring-shape yokes and
heart-shape yokes rotate such that the easy axis is normal to the
film edge.  Permalloy films encapsulated entirely in hardbaked
photoresist are consistently most stable, as compared to other
encapsulation structures involving alumina material.  The uneven
external stress is absorbed by the relatively softer (3) hardbaked
photoresist buffer layer between the alumina overcoat and the
permalloy.

      A better control of the anistropy of the permalloy yoke can be
obtained by placing a hardbaked photoresist buffer layer between the
alumina overcoat and the permalloy.
  References
  (1) D. D. Tang, L. T. Romanklw, "Omega Planar Head Structure
       with 120 Turns, Extended Abstracts," ElectroChemical Society
       184th Meetings, Vol. 93-2, p. 373, 1993.
  (2) C. A. Ross, "Anistropis Stress In Win...