Introduction:

 

The choice of materials for the magnetic recording comes mainly from the control of the magnetic properties suitable for the recording purpose. The magnetic properties of the materials are learned from the magnetic hysteresis (M-H), i.e., the response of the sample magnetization with respect to the change in the applied field. The control of the shape and size of the hysteresis is the heart of designing the materials for magnetic related applications. Numerous magnetic parameters can be extracted from the M-H loop, which are mainly optimized with respect to the fabrication conditions for a particular application. As the study of M-H loops and associate phenomena is very much important, in the next four lectures, we shall cover

1. Magnetic hysteresis loops for recording,

2. Coercivity and remnant flux, slope at coercivity,

3. Effects of switching field distribution on the magnetic properties, and

4. Effects of time and temperature on the stability of the magnetic properties.

(a)	(b)
Figure 35.1: Typical M-H loops of a hard magnetic material with (a) perfect orientation of easy axis perpendicular to the film plane, and (b) considerable random distribution of easy axis.