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Magnetic Annealing of Amorphous Bubble Domain Films

IP.com Disclosure Number: IPCOM000080855D
Original Publication Date: 1974-Feb-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 45K

Publishing Venue

IBM

Related People

Chaudhari, P: AUTHOR [+3]

Abstract

The bubble domain properties of an amorphous magnetic film, such as sputtered amorphous Gd-Co, can be controlled by heat treatment in a magnetic field at a temperature below the crystallization temperature of the film. Annealing in a perpendicular saturation field will in general lower coercivity H(c), and can either increase or decrease anisotropy constant K(u), quality factor Q, and stripe width w(s), depending upon the film composition, annealing temperature, applied magnetic field, and the growth induced anisotropy in the amorphous film. Thus, a post deposition heat treatment in a magnetic field is proposed for changing the properties of amorphous magnetic films.

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Magnetic Annealing of Amorphous Bubble Domain Films

The bubble domain properties of an amorphous magnetic film, such as sputtered amorphous Gd-Co, can be controlled by heat treatment in a magnetic field at a temperature below the crystallization temperature of the film. Annealing in a perpendicular saturation field will in general lower coercivity H(c), and can either increase or decrease anisotropy constant K(u), quality factor Q, and stripe width w(s), depending upon the film composition, annealing temperature, applied magnetic field, and the growth induced anisotropy in the amorphous film. Thus, a post deposition heat treatment in a magnetic field is proposed for changing the properties of amorphous magnetic films.

The data in Tables I and II illustrate these effects. Table I shows the parameters of several Gd-Co amorphous films in the "as deposited" condition and after annealing. Because the growth induced anisotropy is sensitive to deposition conditions, the characteristic length l of the "as deposited" films does not show a simple concentration dependence. The wall energy sigma(w) of these films was also computed from the l parameter and the saturation magnetization 4 pi M(s)/2/.

These results show that the wall energy induced by magnetic annealing increases with increasing Co concentration. The wall energy has a sigma(w) = square root of AK(u) dependence. In the composition range 70-100 atomic % Co, the magnetization at the annealing temperature (200 degrees C) increases with Co concentration. Therefore, it is concluded that the anisotropy induced by annealing is proportional to the magnetization at the annealing temperature.

Reference to Table II shows that an improved coercivity is produced by annealing in an applied field, but such magnetic field is not essential for maintaining growth induced anisotropy.

Annealing in a demegnetized state does not destroy the anisotropy but increases the coercivity. Annealing in a perpendicular saturation field lowers H(c). For this composition, 4 pi M increases with temperature. Since the induced anisotropy follows an M(net).H dependence, higher anisotropies will result for higher annealing temperatures. The higher stripe width sigma(w) for...