Reduced magnetisation

Fig. 61. The variation with temperature of the magnetoelastic stress, MY ( 2 T) multiplied by ( ho + nLuVnHo for Ho,i/Lu 15)50 superlattices. The lines are obtained by adapting reduced-magnetisation power laws, see Del...

Fig. 4.10, instead of in the form of latent heat at the transition. This results in a magnetisation curve with small variations at low temperatures and a large decrease as T approaches Tq, Fig. 4.11. The concepts of reduced magnetisation and reduced temperature, m = M(T)fM(0), and t = T/Tq, respectively, are used to compare materials with different spontaneous magnetisations and Curie points. M T) represents the magnetisation value at temperature T, and M(0) the value at 0 K. Since in ferromagnets magnetisation is always maximum for 0 K, a decreasing curve is obtained.

Fig. 7. Thermomagnetic recording, (a) A focused laser beam generates a thermal profile in the magnetic layer, (b) The coercive force in the layer is reduced and its magnetisation can be reversed by a small magnetic field, here 30 kA/m. At room temperature, the coercive force is high and the written domains are...

If a very high field is appHed the magnetisation can reach its saturated state ia which all the magnetic dipoles are aligned ia the direction of the field. If the magnetic field is switched off, the remanent magnetisation M is left. If the M (or B) is then reduced to sero, a special field strength, the coercivity, is required. 

In these sperimagnetic structures, the subsystem magnetisations are reduced with respect to the collinear magnetic structure in the crystalline compounds. As a consequence, the saturation magnetostriction A.s is decreased. 

---