Collinear magnetic structure

In these sperimagnetic structures, the subsystem magnetisations are reduced with respect to the collinear magnetic structure in the crystalline compounds. As a consequence, the saturation magnetostriction A.s is decreased. 

Driving force for magnetic ordering Classification of ordered (collinear) magnetic structures Models of magnetic ordering CATION... 

NpAl3 is a ferromagnet below Tc = 62.5 K. The magnetic moment value p = 1.2/xB/Np was determined from Mossbauer effect measurements. However, the bulk magnetization does not saturate and a moment of only 0.43/xB/f.u. was observed in a field of 12 T at 4.2 K (Aldred et al. 1974). This discrepancy points to a non-collinear magnetic structure. The non-linearity of the 1 /x versus T curve was tentatively ascribed to crystal-field effects. A strong anisotropy should be considered as an alternative source for the explanation of x(T) measured on a polycrystal. 

As mentioned earlier, the linear exchange interaction between Cu layers cancels due to the bet symmetry, and the actual spin structure is then a result of a delicate balance of superexchange, spin-orbit, and Coulomb exchange interactions (Yildirim et al. 1994, 1996). In the absence of the R ions, quantum fluctuations would be expected to yield the collinear magnetic structure (Yildirim 1999) and this may indeed be the case for the Sr2Cu02Cl2 material (Yildirim et al. 1998). However, this leaves unexplained the... 

X = 0.6 the magnetic ordering changes from antiferro- to ferromagnetic when increasing temperature is observed. The increase in La content leads to ferromagnetism. A collinear magnetic structure was deduced from neutron diffraction data. 

Fig. 4.3 Theoretical Mossbauer spectra on linear and non collinear magnetic structures in presence of external field applied parallel to y-beam random powder in zero-field, ferromagnetic with magnetic moments anti-parallel and parallel to the magnetic moment, and antiferromagnetic structures and non collinear magnetic structures (see text)...

Subsequent neutron diffraction studies showed a collinear magnetic structure for the A = Mn phase but only broad, diffuse scattering for A = Co. The ordered moment for Mn is only 3.7 Pb> much reduced from 5pb expected for S = Another group reported sHghtly different... 

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