Spin polarized neutron scattering

The internal iron (III) ions are octahedrally coordinated by the two oxides and four hydroxo bridges. The outer iron(III) ions coordinate three nitrogens and three hydroxyls. Spin polarized neutron scattering showed that all Fe ions have a spin 5/2, six spins up and two down [23]. This rationalizes the S = 10 spin ground state that is in agreement with magnetization measurements. 

Coherent and isotopic-incoherent scattering involve no spin-flip, whereas spin incoherent scattering (i.e., for hydrogenated molecules) inverts the neutron spin with a probability of 2/3. Since spin-polarized neutrons are used in the neutron spin-echo technique, the polarization of the neutron beam, after spin-incoherent scattering woifld be reversed and three times less intense. 

Figure 6. Polarized neutron reflectivities of fN 0 = 5 nm, 20 nm and 60 nm samples during the reversal process. The spin flip (R+, R +) and non spin flip (if4-1", R") reflectivities are simultaneously modeled to obtain the magnetization configuration as shown in the inset. The lines are the computed reflectivities for different scattering cross-sections based on this model.

The analysis of the polarised neutron experiment on K2NaCrFe (Fig. 9) has been completed< >. The aspherical form factor component/4(0 was shown to be particularly sensitive to the covalent spin distribution, and the shape of fi Q) supported the inference for eg spin polarization drawn from the comparison of powder neutron diffraction data and resonance data (Section VI. B). A preliminary report of the form factor determination for both tetra-hedrally and octahedrally coordinated Fe + in YaFesOis by polarized neutrons has been given ). The form factors are not the same and that for tetrahedral Fe + is contracted relative to that for octahedral Fe +, which follows closely the calculated free-ion curve. The ligand forward peak (Section VI. B) has been directly observed ) in a measurement of the critical scattering of neutrons by ferromagnetic K2CUF4. 

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