Maximum magnetic permeability

It should be noted from Figure 9.12 that the magnetic permeability increases as the effective aspect ratio increases. Conductive thermoplastics, which contain carbon fiber, have a maximum injection rate above which electric conductivity will not increase. These composites also depend on fiber orientation which increases the... 

Fig. 4.39. Magnetic permeability of YIG as a function of applied field the maximum value is (Globus, Duplex Guyot, 1971).

Optimal conditions conespond to a magnetic excitation value such as permeability of the material is maximum. 

A quantitative study of the process indicates that, as the field intensity H increases, the magnetic induction B also increases in a manner characteristic of the substance, This is conveniently represented by a graph, which is called the magnetization curve. See Fig. 1. Its initial slope is the initial permeability (/Xo). If H is carried to some maximum value H , and then reduced (to - //,), R follows the dotted hysteresis curve. B does not fall off as it was built up (solid line) the residual induction B, is... 

The advantages of the latter property are manifold. Not only can the magnetization vector be considered as rigid, also the surface current density is constant. Its maximum value equals about 7000 A/cm for Sm-Co material and is approximately 10000 A/cm for Nd-Fe-B material. Furthermore, the permanent magnet properties are not perturbed by common external magnetic fields, and the relative permeability is constant and of the order of 1. 

The basic magnetic properties expected in soft magnets are high initial and maximum permeabilities, p-, and r,., and low coercivity, (lower than 10 A/m). In many applications, soft magnets are subjected to ac fields their frequency response and, particularly, their ac losses are therefore important. 

Table. 3-17 Standard lEC specification for grain-oriented magnetic steel sheet (a) normal material (b) material with reduced loss (c) high-permeability material. The conventional designation of the various grades (first column) includes, from left to right, (1) 100 times the maximum power loss, in (Wkg ), at 1.5 T (a) or 1.7 T (b,c) peak induction (2) 100 times the nominal sheet thickness, in (mm) (3) the letter N for the nominal material (a), or S for material with reduced loss (b), or P for high-permeability material (c) (4) one tenth of the frequency in Hz, at which the magnetic properties are specified [3.7] ...

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