M ferrites

The intrinsic properties may be modified by substitution (31). Ba can be fuUy replaced by Sr or Pb and partly by Ca (<40 mol %). CaM, stabilized with 0.03 mol % La202, is also possible. The intrinsic properties of these M-ferrites vary somewhat and other factors such as sintering behavior and price of raw materials often dictate the commercial viabiUty. Large-scale production is concentrated on BaM and SrM. High quaUty magnets are generally based on SrM, and somewhat lower priced magnets are based on BaM. 

Since the 1960s, the quaUty of M-ferrite manufactured has improved continuously, while the price has decreased considerably. Decisive progress in quahty was obtained by the appHcation of sinter additives (90), the introduction of pressing in a magnetic field (23), and the use of Sr instead of Ba, in combination with a sophisticated appHcation of Si02 (91,92). Important contributions to price reduction came from the development of fast multiple-die... 

Fig. 9. Demagnetization curves for M-ferrites at high K values (see Table 8).

A variety of shapes and sizes exists for the commercial M-magnets. Most M-ferrite products are flat owing to the relatively high and moderate B. Basic shape groups are rings, disks, plates, rods, cylinders, blocks, strips, and segments. Each shape-group in turn contains a number of products. The... 

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