Ferromagnetic resonance spectra

Figure 5.22 Ferro- and paramagnetic resonance spectra for a nominal 2at.% Mn- doped ZnO pellet (a) Ferromagnetic resonance spectra for a sample sintered at 500°C. (b) Room-temperature paramagnetic resonance spectra for the same sample sintered at 900 C. (After Ref. [16].)...

FIGURE 3.16 The effect of a tiny ferromagnetic particle on the proton resonance spectrum of cellobiose octaacetate. The top spectra are run with the particles present the bottom curves are the spectra with the particle removed. 

As mentioned above, the molecular fields in ferromagnetic crystals are extremely inhomogeneous, and therefore the nuclei in different crystallographic positions are affected by fields with different magnitudes and directions. So the nuclei have different resonance frequencies, which form a broad NMR spectrum. In the present subsection we shall consider the separate line width of the proton resonance spectrum in ethylsulfates. 

The noise power spectrum is proportional to x(o)) 12. Experimental measurements have verified that the magnetic fluctuations take the spectral shape of the ferromagnetic resonance, as shown in Eigure 5. 

F.6. Mossbauer Spectroscopy F.6.1. Introduction F.6.2. The Mossbauer Spectrum F.6.3. Bulk and Surface Static Studies F.6.4. Superparamagnetic Relaxation in Zero Applied Field F.6.5. Influence of a Large Applied Field F.6.6. Influence of a Medium Applied Field F.6.7. Concluding Remarks F.7. Ferromagnetic Resonance F.8. Neutron Experiments... 

Thereafter, crystals were brought back to the aerobic 25% MPD solution, buffered with 50 mAf sodium phosphate, pH 5.5. This procedure is based on Avigliano et al. s (157) method of preparing T2D ascorbate oxidase in solution and was modified by Merli et al. (159) for use with ascorbate oxidase crystals. The 2.5-A-resolution X-ray structure analysis by difference-Fourier techniques and crystallographic refinement shows that about 1.3 copper ions per ascorbate oxidase monomer are removed. The copper is lost from all three copper sites of the trinuclear copper species, whereby the EPR-active type-2 copper is the most depleted (see Fig. 10). Type-1 copper is not affected. The EPR spectra from polycrystalline samples of the respective native and T2D ascorbate oxidase were recorded. The native spectrum exhibits the type-1 and type-2 EPR signals in a ratio of about 1 1, as expected from the crystal structure. The T2D spectrum reveals the characteristic resonances of the type-1 copper center, also observed for T2D ascorbate oxidase in frozen solution, and the complete disappearance of the spectroscopic type-2 copper. This observation indicates preferential formation of a Cu-depleted form with the holes equally distributed over all three copper sites. Each of these Cu-depleted species may represent an anti-ferromagnetically coupled copper pair that is EPR-silent and that could explain the disappearance of the type-2 EPR signal. 

The addition of azide to deoxyHr yields deoxyHrN3, which has a paramagnetic ground state based on MCD spectra (49). The MCD analysis suggests that the iron centers have become weakly ferromagnetically coupled. Its NMR spectrum shows His N-H resonances at 47, 67, and 78 ppm in a 1 3 1 intensity ratio (35). Presumably, the spectral changes are a result of the difference in the coupling interaction and the presumed alteration... 

Rode et al. (107) carried out an electron spin resonance study of the intermediate oxides formed in the thermal decomposition of chromic anhydride. Chromium decachromate, chromium dichromate, and chromium hydroxide at room temperature, as well as the ferromagnetic compounds chromium monochromate and chromium dioxide above their Curie points at 130°, give symmetrical absorption lines 130 to 160 gauss wide with a g factor of 1.97, Shnkin and Fedorovskaia (108) studied CrgOa containing lithium, and detected fine structure in the ESR spectrum. 

Often ftrlly reduced samples of dinuclear iron containing proteins contain a ferromagnetically coupled dinuclear Fe " center that has as its ground state 5tot= 4 vide infra). In many cases formally forbidden AMs= 4 transitions between the Mg = 2 spin states produce resonances in the EPR spectrum with geff 16 (Fig. 5). 

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