Browse Prior Art Database

Magnetic Head

IP.com Disclosure Number: IPCOM000073377D
Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Thornley, RF: AUTHOR

Abstract

Constant output signals independent of tape speed may be obtained from a magnetic tape head by inserting a section of square loop material in an otherwise conventional magnetic path. If an element of tape of width L, length lambda/2, and magnetized thickness d has a coercivity of H(t) and a remanence of B(t), then the maximum possible magneto motive force is H(t) lambda/2 and the maximum flux available is B(t)Ld. The source reluctance is given by: R = H(t) lambda/2 B(t)Ld. For maximum energy transfer, the reluctance of the square loop material, before it switches, must equal the tape reluctance. If the switching material has length 1, width L and thickness w, then its reluctance is 1/Lw. For optimum matching 1/Lw = H(t) lambda/2 B(t)Ld. For most recording tapes, demagnetizing effects make lambda/2 approximately d . .

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Magnetic Head

Constant output signals independent of tape speed may be obtained from a magnetic tape head by inserting a section of square loop material in an otherwise conventional magnetic path. If an element of tape of width L, length lambda/2, and magnetized thickness d has a coercivity of H(t) and a remanence of B(t), then the maximum possible magneto motive force is H(t) lambda/2 and the maximum flux available is B(t)Ld. The source reluctance is given by: R = H(t) lambda/2 B(t)Ld. For maximum energy transfer, the reluctance of the square loop material, before it switches, must equal the tape reluctance. If the switching material has length 1, width L and thickness w, then its reluctance is 1/Lw. For optimum matching 1/Lw = H(t) lambda/2 B(t)Ld. For most recording tapes, demagnetizing effects make lambda/2 approximately d . . 1/w = H(t)/B(t).

For maximum energy transfer, the coercivity H(s) of the switching material must be chosen so that it just switches at the peak of the input tape field, i.e., when H(t)lambda/4 = H(s)1 . . H(s) = H(t)lambda/41.

Applying these results to a typical system in which H(t) = 250 oe, B = 1000 gauss, lambda = 2 mils (1000 fr/in.), and assuming that the minimum practical thickness of the square loop material is 20 mils, then the switching element length is 5 mils and the coercivity is 25 oe. These dimensions are readily attainable with existing ferrite materials.

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