Magnetic head employing easy axis thin film inductor

• US 4,120,011 A
• Filed: 09/21/1977
• Issued: 10/10/1978
• Est. Priority Date: 09/21/1977
• Status: Expired due to Term

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Kolb, Frederick John Jr.
• Primary Examiner(s): Wolff, John H.
• Application Number:
  US05/835,106
• Time in Patent Office: 384 Days
• Field of Search: 360/111-113, 360/122, 360/125, 324/43 R, 324/0.5 R
• US Class Current: 360/111
• CPC Class Codes: G11B 5/335 with saturated jig, e.g. for detecting second harmonic; balanced flux head

Abstract

A flux-sensitive magnetic head employs, at its back part, a structure having a thin single domain magnetic film coated thereon. A first coil wraps around the coated structure; and a second coil wraps around one pole of the head. A direct current is passed through the second coil, thereby to apply an easy axis magnetic bias to the film. By appropriately contouring the back gap of the head, signal flux appearing at the head front gap asserts a differential magnetic force to the easy axis of the film, thereby causing the inductance of the first coil to vary detectably.

Claims

1. Magnetic head apparatus for use in detecting signal flux comprising:

a. first and second magnetic pole pieces disposed to form a transducer gap and a back gap therebetween;

b. wedge-like means at said back gap for providing a gradually changing reluctance across said back gap;

c. elongated sense element means within said back gap, said sense element means having an essentially single domain magnetic film thereon, said film being magnetically coupled to said pole pieces for completing a magnetic circuit comprising said pole pieces, said transducer gap, and said film, said film being so disposed on said sense element means that the easy axis of said film is about the longitudinal axis of said sense element means and also substantially parallel to said transucer gap, said sense element means being disposed within said back gap said head apparatus being adapted to have a bias field applied across said back gap, the field extending across said back gap being applied differentially to the easy axis of said film; and

d. a sense coil inductively coupled to the easy axis of said sense element means;

whereby signal flux entering said transducer gap correspondingly causes the inductance of said sense coil to vary, and whereby variation in said sense coil inductance may be converted to an electrical signal corresponding to said inductance variation.

2. The apparatus of claim 1 wherein said sense element means is a wire having a magnetic film coated thereon.

3. The apparatus of claim 1 including means for applying a bias field across said back gap.

4. The apparatus of claim 1 wherein said means at said back gap for providing a gradually changing reluctance across said back gap comprises the parts of said first and second pole pieces which form said back gap, said parts being contoured so as to provide a varying dimension across said back gap.