Spontaneous volume magnetostriction

High-temperature slope of the thermal expansion (a, in K 1), total spontaneous volume magnetostriction at 4.2 K (us) and relative contributions to s of the 3d and 4f sublattices ( sd and usf) in various R2Fe)4B compounds. (After Buschow and Grossinger 1987.)... 

Fig. 34. Spontaneous volume magnetostriction as a function of temperature in various R2Fe14B compounds. The corresponding Curie temperatures are indicated by arrows. (After Buschow and...

The results obtained for the compounds of the series Rj Fe 4C confirmed the results on the isotypic R2Fej4B compounds, showing that the spontaneous volume magnetostriction extends to temperatures substantially above in this type of ternary compounds. This observation lends credence to the view that the local iron moments in iron-based metallic materials do not disappear above (Holden et al. 1984),... 

Fig. 4.3-33 (a) Schematic diagram of invar-type thermal-expansion anomaly. The dashed curve indicates thermal expansion for hypothetical paramagnetic state. The difference between the two curves corresponds to the spontaneous volume magnetostriction, ah. (b) Temperature dependence of the spontaneous magnetization... 

Fig. 8. Temperature dependence of the magnetic contribution to the spontaneous volume magnetostriction of the RC02 compounds. The arrows indicate the Curie temperatures (Minakata et al. 1976).

FIGURE 66 Temperature dependence of the spontaneous volume magnetostriction o)s of GdAl2 at high pressure. The inset shows coj at 77.4 K at high pressure (Fuchizaki et al, 2006). 

The exchange interactions are isotropic to first order. They describe a coupling between the magnetic moments and dominate the magnetic ordering in the materials. The variation of these interactions with the interatomic distance is the reason for a spontaneous deformation (i.e., the volume magnetostriction). 

The spontaneous magnetostriction has been measured by single crystal x-ray diffraction between 10 and 300 K (Kusz et al. 2000). As can be seen from figs 38 and 39, both compounds show pronounced linear as well as volume effects. Gd3Ni is characterized by a large positive spontaneous magnetostriction in a-direction (the estimated value at 0 K is (Aa/a)mag 2.9 x 10 3), whereas the effects in b- and c-direction are about two... 

Magnetic properties of Zr(Fe1 xCo t)2. a is the volume saturation magnetization, Tc the Curie temperature, 8p the paramagnetic Curie temperature, C the Curie constant, y the electronic specific heat coefficient, //hyp the hyperfine field, and us the spontaneous magnetostriction coefficient. 

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