Magnetic structures examples

Ca2pe205. Geller et al, (15) and Gonser et al. (19) have recently used the Mossbauer effect to study Ga2Fc20r>. This study is an example of how the Mossbauer effect in conjunction with crystal chemical arguments can be used to work out the magnetic structure of a material without using neutron spectroscopy. 

The first condition concerns the electronic configuration of the cations, the second one the arrangement of ions in the lattice, the crystal structure. Depending on the combination of those different factors, superexchange may occur in 3, 2 or 1 dimensions or fail to appear. Examples of all these four cases wiU be discussed in the following in context with the magnetic structures of fluorides. 

Using unpolarized neutrons, q p averages to zero and the study of the elastic magnetic cross section p q allows, in principle, to determine the magnetic structure. However, this determination may not be complete (for example the phase between the different harmonics cannot be determined from neutron diffraction experiments). Different magnetic structures, with different domain population may also lead to the same... 

Recent advances in the development of non-invasive, in situ spectroscopic scanned-probe and microscopy techniques have been applied successfully to study mineral particles in aqueous suspension (Hawthorne, 1988 Hochella and White, 1990). In situ spectroscopic methods often utilise molecular probes that have diagnostic properties sensitive to changes in short-range molecular environments. At the particle-solution interface, the molecular environment around a probe species is perturbed, and the diagnostic properties of the probe, which can be either optical or magnetic, then report back on surface molecular structure. Examples of in situ probe approaches that have been used fruitfully include electron spin resonance (ESR) and nuclear magnetic resonance (NMR) spin-probe studies perturbed vibrational probe (Raman and Fourier-transform IR) studies and X-ray absorption (Hawthorne, 1988 Hochella and White, 1990 Charletand Manceau, 1993 Johnston et al., 1993). 

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