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Temperature Biasing for Magneto Optical Recording

IP.com Disclosure Number: IPCOM000076134D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 24K

Publishing Venue

IBM

Related People

Lee, K: AUTHOR [+2]

Abstract

Magneto-optical memory operation may be described in terms of the magnetization M versus temperature T graph shown in Fig. 1. At the ambient temperature T(a) a memory bit is read using the magneto-optical rotation theta(A) which is proportional to the magnetization. The magnitude of theta(A) is therefore important for reading efficiency. For Curie temperature writing the film is heated above the Curie temperature TC. The required heating energy is proportional to the temperature interval TC-Ta, and therefore the magnitude of TC-Ta is important for writing efficiency.

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Temperature Biasing for Magneto Optical Recording

Magneto-optical memory operation may be described in terms of the magnetization M versus temperature T graph shown in Fig. 1. At the ambient temperature T(a) a memory bit is read using the magneto-optical rotation theta(A) which is proportional to the magnetization. The magnitude of theta(A) is therefore important for reading efficiency. For Curie temperature writing the film is heated above the Curie temperature TC. The required heating energy is proportional to the temperature interval TC-Ta, and therefore the magnitude of TC-Ta is important for writing efficiency.

Ideally it is preferred to have large theta(A) and small TC-T(a). However, conventional temperature biasing raises T(a) closer to TC (e.g., to T(a)') thus reducing theta.

The method below uses selective temperature biasing. Let T(a) = 20 degrees C. Let TC be well above room temperature (e.g., 200-400 degrees C) in order to obtain large theta(A) at T(a). Then, using an auxiliary light source the magnetic film is temperature biased to temperature T(a)' (see Fig. 1) for writing, and temperature unbiased for reading at temperature T(a). The selective biasing is done using an auxiliary light source, such as a tungsten lamp, focused on a narrow strip 6 of a memory disk, as shown in Fig. 2. Thus, as the disk rotates, a bit area 6 to be written is first heated up from T(a) to T(a)' by the auxiliary source and then heated from T(a)' to TC by the laser 5. For r...