Coercive force, intrinsic

Magnet Applications. For magnets of the type FeNdB, a small amount of gallium is effective in improving the intrinsic coercive force (53). It slows the pinning type recoil loop. The thermal stabiUty is increased. The irreversible loss is less than 1.5% under 373 K (1000 h). 

The effect of a variable Nd and B concentration was extensively investigated by Sagawa et al. (1984a). They found that the remanence Br shows a comparatively small concentration dependence. By contrast, the intrinsic coercive force jHc depends strongly on the Fe concentration. The marked decrease of the maximum energy product ( BZf)max observed for high Fe concentrations is mainly due to the rapid decrease of jHc in this concentration range. This behaviour may be under-... 

Fig. 40. Intrinsic coercive force after sintering at Tsi = 1080 ° C followed by various heat treatments, (a) sintering at 1080 0 C and quenching in oil. (b) same as (a) followed by heating at T, = 900° C for 2 h and quenching in oil. (c) same as (a) followed by heating at 900° C for 2 h and cooling to room temperature, (d) same as (c) followed by heating at T2 for 1 h and quenching in water. (After Tokunaga et al. 1986.)...

In section 3.2 it was mentioned that, in addition to a large maximum energy product, a high intrinsic coercive force jHc is needed in some applications. Moreover, the maximum energy product (BH)max itself depends on the coercive force and may become lower than the theoretical limit (Z 77)max = Bt bHc = Js2/4/jl0 if bHc falls appreciably below the value Js/n0. It is desirable therefore to have some understanding of the mechanisms that determine the ultimate magnitude of the coercive force in permanent magnets. 

Fig. 1. Chronology of magnet development since 1900 Best reported laboratory values for the static energy product and intrinsic coercive force. (After Strnat 1986.)...

Finally, there must be a mechanism for creating a sufficiently high intrinsic coercive force, MHC. What is sufficient depends again on application requirements, but for modem magnet materials it is usually defined as MHC = jBis, the minimum value that permits a close approach to the theoretical energy product limit, (2ttMs)2 = ( BJ2. 

In this chapter Hc is usually used to mean the intrinsic coercive force, mHc or Hc]. The induction coercive force is always abbreviated BHC. 

Fig. 14. Deterioration of the intrinsic coercive force of several RE-TM alloy powders during short-term exposure to air at elevated temperature. (After Stmat 1970.)...

Fig. 29. Dependence of the intrinsic coercive force of sintered and quenched SmCo5 magnets on the temperature of the post-sintering anneal. (After Paladino et al. 1975.)...

Magnet type Remanence (mT) Depending on the variety Intrinsic coercive force, Hci (kA/m) Depending on the variety Maximum operating temperature (°C) Depending on the variety... 

Magnet Remanence, Bj Intrinsic coercive force. Maximum operating... 

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