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Several zirconium phosphate (ZrP) gels of various water contents produced by a sol - gel method were investigated. They were found to be the polymer-class gels using the method of small-angle neutron scattering. X-ray diffraction analysis revealed that their solid-phase framework was formed from branched fragments (layers and blocks) of -ZrP crystal structure. These gels are strongly fluctuating systems when they are on the scale of . Their fluctuation character is shown to be described by two parameters: a correlation radius and a fractal dimension D. It was found that and almost did not depend on the water content and that D increased from to when the water content decreased from 50% to 0% as the gels were dried to a temperature of . Simultaneously, substantial shrinkage of granules, a decrease in porosity and ion-exchange capability, and formation of blocks from -phosphate layers occurred with decrease in the water of the hydrogel as it dried. A probable description of the evolution of the ZrP-gel structure with variation in the water content during drying is suggested on the basis of the data obtained.

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a b s t r a c tMagnetic susceptibility, magnetization and neutron diffraction measurements have been performed to study structure and magnetic states of crystalline and amorphous Nd 2 Fe 14 B and Er 2 Fe 14 B alloys. In the crystalline state there exists a large (about 20%) anisotropy of Er-sublattice magnetization. Values of the magnetic anisotropy constant of Er ions and the Er-Fe exchange-coupling parameter were estimated using temperature dependence of the Er-and Fe-sublattice magnetizations. Amorphous state of the samples was obtained by irradiation of fast (E eff P 1 MeV) neutrons with a fluence up to the 1.2 Â 10 20 n/cm À2 at 340 K. It is shown that antiferromagnetic coupling between the rare-earth and iron spins is kept in the amorphous state. Amorphization of the samples is found to result in reduction of the Curie temperature (T C ) by about 200 K and almost total absence of coercivity. We suggest that the strong decrease of T C is a consequence of enhancement of negative Fe-Fe interactions as a result of dispersion of interatomic distances, which is a characteristic feature of the amorphous state.