Magnetostriction in nanocrystalline

Fig. 70. Saturation magnetostriction, versus nanocrystalline fraction in Fe73 5Cu Nl>3Sii3B9 alloys. The numbers 1.2,3 denote the different contributions according to eq. (34). After Szymczak (1999) and refs therein.

The existence of the surface contribution to the effective magnetostriction of nanocrystalline alloys has been confirmed theoretically in terms of the dipolar model (Szumiata et al. 1999). These authors showed that, due to the limited radius of the nanoparticles, additional magnetostrictive stresses are localised at the interfaces. The evaluation of the influence of the dipolar interaction on the magnetostriction in crystalline grains of perfect spherical shape surrounded by a magnetic environment of about 0.S nm with either crystalline or amorphous structure has been calculated. A similar method was previously used to obtain the surface and volume anisotropy (Draaisma and de Jonge 1988) and to... 

Fig. 67. The saturation magnetostriction, Ag, of Fe-Cu-Nb-Si-B alloys (a) influence of the annealing temperature and (b) influence of the Si content in the nanocrystalline state. The figure includes the data for Fe-Nb-B (A) and Fe-(Cu)-Zr-B (A) alloys. After Herzer (1997) and refs therein.

Fig. 69. Saturation magnetostriction, Ag, versus crystalline fraction, p, in (a) Fe89Zr7B4 and (b) FegjZr7B6Cu2 nanocrystalline alloys. After Slawska-Waniewska et al. (1996).

The behaviour of As can be understood from the balance of magnetostriction among the structural phases present in the nanocrystalline state, i.e. [12]... 

The role of the unconventional radio frequency Mossbauer technique [143] has to be emphasized in the case of the nanocrystalline alloys indeed, it allows to distinguish the magnetically soft amorphous and nanocrystalline phase from the magnetically harder microcrystalline Fe, to determine the anisotropy helds in each phase as a function of the rf held intensity. It was found that the magnetic anisotropy of the amorphous matrix is signihcantly smaller than that encountered in the nanocrystalline phase. Finally, the rf sidebands effect reveals a strong reduction of magnetostriction related to the formation of the nanocrystalline phase [144, 145]. 

---