Spiral magnetic structure

A slightly different type of form-factor measurement was performed by Felcher et al. (1976) who performed an experiment to look specifically at the aspherical component of the form factor of Ho. (The measurements were performed both for a pure Ho crystal and a H00.9SC0.1 alloy.) They showed that for a spiral magnetic structure of ions having aspherical magnetization distributions, the form factor for ions in the /th layer at a given Q was given by... 

Fig. 39. The different magnetic structures of HoNi2 B2C as determined by neutron scattering, (a) Commensurate antiferromagnetic, (b) incommensurate restructure (spiral) with the modulation vector T2 = (0.0,0.916) and (c) proposal how the incommensurate a -structure looks like (Loewenhaupt et al. 1997). Its modulation vector is...

Figure 3.4 Examples of magnetic structures. In all cases the orientation of the lattice is similar, except in the second view of (b), where the point of view is nearly along a. (a) Sinusoidal structure with propagation vector k = (0,, 0) and Sk = (0,0,w). (b) Helical, or spiral, structure with propagation vector k = (0,(5,0) and Sk = (w/,0,w). (c) Cycloidal structure with propagation vector k = (0,, 0) and Sk = (0,u,ui).

Figure 7.14. Total energy calculations of different magnetic structures for an FeNi alloy with 10% Ni. SWS denotes the Wigner-Seitz radius. The inset shows the q vector of the spin spiral and the moment of the alloy components in the spin spiral structure as functions of volume.

Magnetic structure parameters for Co Ni MnGe. The angles define the spiral axis and the t s are the components of the spiral vector (Niziol et al. 1982). 

One of the best resolved Au magnetic spectra is that of Au2Mn at 4-2 K, which is illustrated in Fig. 16.28 [98]. The eight allowed lines for a I transition with E2 admixture are clearly shown, and the asymmetry in the spectrum is due to the presence of a quadrupole interaction (e qQ = 2-705(70) mm s ), which is directed perpendicular to the magnetic axis Httt = 1571 kG). An unusually large pressure dependence of the magnetic field was interpreted as due to the uncoiling of the spiral spin structure of the alloy. 

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