Nanocrystalline Soft Magnetic Alloys

The evolution of the nanocrystalline state during annealing occurs by partial crystallization into randomly oriented, ultrafine bcc a-Fe—Si grains that are 

It is useful to note the influence of the atomic diameter of alloying additions on the grain size of the a-Fe—Si phase starting from the classical alloy composition Fe73.5Sii5.5B7CuiNb3. This effect is shown for 

One of the decisive requirements for excellent soft magnetic properties is the absence of magnetostriction. Amorphous Fe—Si—B—Cu—Nb alloys have a saturation 

This behavior is caused by the compensation of the negative saturation magnetostriction kg of the a-Fe—Si phase As —8 X 10 and the positve values of kg of the residual amorphous phase of As - - 24x 10 . 

Typical commercial grades for low remanence hysteresis loops, Vacuumschmelze GmbH 1990, 1993 [3.37,38] 

The influence of the annealing temperature on grain size, He, and iii of a nanocrystalline type alloy is shown in Fig. 4.3-23 [3.23], 

A = exchange stiffness constant. A schematic representation of this model is given in Fig. 4.3-27. The basic effect of decreasing the grain size consists of local averaging of the magnetocrystalline anisotropy energy Ki for D = 10-15 nm at Lq = 30-50 nm (about equal to 

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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...

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]...

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. 

H. Herzer Nanocrystalline Soft Magnetic Alloys. In Handbook of Magnetic Materials, ed. by K. H. J. Buschow (Elsevier, Amsterdam 1997) pp. A16-A62... 

Dr.-Ing. habil. Manfred Muller is a Professor emeritus of Special Materials at the Institute of Materials Science of the Dresden University of Technology. Before his retirement he was for many years head of department for special materials at the Central Institute for Solid State Physics and Materials Research of the Academy of Sciences in Dresden, Germany. His main field was the research and development of metallic materials with en hasis on special physical properties, such as soft and hard magnetic, electrical and thermoelastic properties. His last field of research was amorphous and nanocrystalline soft magnetic alloys. He is a member of the German Society of Materials Science (DGM) and was a member of the Advisary Board of DGM. 

G. Herzer, in Nanocrystalline soft magnetic alloys. Handbook of Magnetic Materials vol. 10 ed by K.H.J. Buschow (Elsevier Science, 1997), pp. 415-462)... 

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