Energy product, magnetic

Lidong et al. (1985) studied the system PrjgFeg4 j,B in order to produce permanent magnets. Energy products in excess of 300kJ/m were obtained. 

H, for which J = 0, is the intrinsic coercivity whereas the usual coercivity, for which S = 0, is denoted by H or H. For permanent magnets, the value (BH), the maximum energy product, is an important measure of quaHty. The value (BH), iadicated ia the secoad quadrant of Figure 1, represents the poiat of maximum efficieacy where a givea amouat of magnetic flux is produced by the smallest amouat of material. 

Fig. 9. Progress in energy product for hard magnetic materials. To convert to cal, divide by 4.184.

The energy product is a measure of a magnet s resistance to demagnetisation in reverse fields, thus a high coercivity along with the... 

Magnet Type Maximum Energy Product kJ /m Remanence Br T Coercivity bHc kA/m... 

The importance of improved magneiie alloys is sometimes underestimated. Magnets are used widely in telecommunications and in scores of electrical and electronic instruments and appliances, and it has been estimated thal the demand lor permanent magnets has increased by a factor of three since 197(1. Chromium-cohall-iron alloys have increased markedly in application. It is interesting to note thal these magnets have essentially about Uve same coercive force and maximum energy product as Alnico 5. but with only half the cohall content. 

The operating state of a permanent magnet lies in the second quadrant of a B-H hysteresis loop since the magnet is always subject to its own demagnetizing field. Apart from its coercivity and remanence, a permanent magnet material is rated by its maximum energy product ... 

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