Ferrites Curie temperature

The spinel ferrites were fabricated by solid state reaction technique. Cobalt and Zinc ferrites CoxZnyFe204,(x=0.7,0.3,0.4,0.2 and y=0.3,0.7,0.6,0.8) were prepared by solid state reaction technique. The crystalline structure of the sample was investigated by X-ray diffraction(XRD). All samples show cubic spinel structure. The lattice parameter decreases with increasing cobalt content. Magnetic properties shows that the prepared sample exhibit ferromagnetic behaviour at room temperature. The saturation magnetization increases with increasing cobalt content. Curie temperature... 

Lithium ferrite itself (x = 0.5) has a high Curie temperature and can be fabricated so as to give a square hysteresis loop satisfactory for digital-computer memory cores. In this application, the dielectric losses connected with the presence of mobile charge carriers can cause a dramatic loss in core quality. The mobile carriers may be introduced by... 

The minor ferromagnetic phase that was evident in some samples from the Curie temperature of 423 K was assumed to be attributable to potassium ferrite, K2O Fe203 0 = 423 K) (I). The amount of this phase indicates that the K2O that was added as a promoter is mostly tied up with an iron oxide. 

Table 4.13. Curie temperature and saturation magnetisation of some hexagonal ferrites.

The last step is a reoxidation to y-Fe20 at 250 °C. The particle dimensions vary from 0.25 to 0.75 pm in length, and 0.05-0.15 pm in width, with a coercive field of 20-24 kA/m and a saturation magnetisation of 370 kA/m. Since the Curie temperature is one of the highest amongst the ferrites (> 600°C), the temperature dependence of all the magnetic properties is quite small. 

Because of their high Curie temperature ( 1070K) and thermal stability, Alnico materials are used in high-temperature applications and measuring instruments. They are also used in loudspeakers, but strong competition from cheaper hexagonal ferrites is decreasing their share of this market. 

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