Soft magnetic alloys

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

Energy losses in soft magnetic materials arise due to both hysteresis and eddy currents, as described in the previous section. Eddy current losses can be reduced by increasing the electrical resistivity of the magnetic material. This is one reason why solid-solution iron-silicon alloys ( 4% Si) are used at power frequencies of around 60 Hz and why iron-nickel alloys are used at audio frequencies. Some magnetically soft ferrites (see Section 6.2.2.1) are very nearly electrical insulators and are thus immune to eddy current losses. Some common soft magnetic materials and their properties are listed in Table 6.19. Soft magnetic alloys are described further in Section 6.2.1.6. 

Y.Yoshizawa, S. Oguma, and K. Yamauchi, New Fe-Based Soft Magnetic Alloys Composed of Ultrafine Grain Structure , J. Appl. Phys. 64, 6044 (1988). 

Figures 4(a) and 4(b) show the relationship between the average grain size and the coercivity in various Fe-based nanocrystalline soft magnetic alloys prepared by crystallization of amorphous precursors (For details, see Herzer [13], Yoshizawa [31], Muller and Mattem [32], Fujii et al. [33], and Suzuki et al. [34, 35]). As shown in Fig. 4(a), the coercivity Ha of the nanocrystalline Fe-Si-B-M-Cu (M = IVa to Via metal) alloys follows the predicted D6 dependence in a D range below LO ( 30 to 40 nm for this alloy system) although the plots deviate from the predicted D6 law in the range below H0 1 A/m where the effect of grain refinement on is overshadowed by magneto-elastic and annealing induced anisotropies. Hence, the experiments are better described by Hc [a2 + where a...

High-Performance Soft Magnetic Alloy Films Prepared by Electrodeposition... 

Yoshizawa Y et al (1988) New Ee-based soft magnetic-alloys composed of ultrafine grain-structure. J Appl Phys 64 6044-6046... 

Fig. 13.18 Simplified processs schematic showing the major steps for fabrication and assembly of the MEMS FDNMR spectrometer. The steps involve electropating of a thin-film, multi-component, soft magnet alloy, fabrication of the Si beam resonator, and the final assembly of the spectrometer. Shown to the right are an optical micrograph of the electroplated 60 pm detector magnet, and an SEM image of the 400-pm-long Si beam resonator fabricated using Deep Reactive Ion Etching...

Permendur FeCo(-2V) soft magnetic alloy Bozorth (1951), Chen (1961)... 

The fee phase in the Ni—Fe alloy system and the formation of the ordered NisFe phase provide a wide range of structural and magnetic properties for developing soft magnetic materials with specific characteristics for different applications. The phase diagram is shown in Sect. 3.1.5. Before amorphous and nanocrystalline soft magnetic alloys were introduced, the Ni—Fe materials... 

Fig. A.3-23 Average grain size, coercivity and initial permeability of a nanocrystalline soft magnetic alloy as a function of the annealing temperature [3.23]...

Table 4.3-24 shows the magnetic and physical properties of some commercially-available nanocrystalline alloys for conqtarison to amorphous and Ni—Fe-based crystalline soft magnetic alloys. Magnetic field annealing allows the shape of the hysteresis loops of... 

Flg.it.3-29a,b Soft magnetic alloys with flat hysteresis loops (a) Crystalline, (b) Amorphous and nanocrys-taUine (curve indicated by n) [3.12]... 

A survey of the field dependence of the amplitude permeability of various crystalline, amorphous, and nanocrystalline soft magnetic alloys is given in Fig.4.3-31 [3.12]. Figure 4.3-32 [3.23] represents the frequency behavior of the permeability jx of different soft magnetic materials for coirparison. 

Fig. 4.3-31 Amplitude permeabUity-field strength curves of soft magnetic alloys (/ = 50 Hz) amorphous (a) nanocrystalline ( ) [3.12]...

---