Superspinglass state in functionalized zeolite 5A-maghemite nanoparticles

The structural, vibrational, and magnetic properties of maghemite nanoparticles functionalized with zeolite type 5A and synthesized by coprecipitation were studied in detail. Crystallite and particle sizes were determined and discussed based on the polydispersity index. Its value of 0.4 has suggested the presence of a broad particle distribution with particle sizes between 3 and 20 nm. Three samples were successfully functionalized either before or after the formation of the maghemite nanoparticles. Infrared studies have shown that the functionalization has occurred by hydrated surface groups present in the zeolite type 5A surface, which have favored strong bindings and highly concentrated regions of maghemite nanoparticles. From the temperature dependence of the hyperfine magnetic field obtained by Mossbauer spectroscopy, the effective magnetocrystalline anisotropy constants of the three nanohybrids were determined. They are one order of magnitude higher than for the bulk counterpart, and there is evidence for strong interparticle interactions for the three studied nanohybrids. These strong magnetic interactions of the nanoparticles in the zeolite framework have favored a superspinglass-like behavior for all samples with transition temperatures located at 74 and 208 K, as confirmed by AC susceptibility measurements.

Automated summary

The study investigated the structural, vibrational, and magnetic properties of maghemite nanoparticles functionalized with zeolite 5A. The research found strong bindings between hydrated surface groups of zeolite 5A and maghemite nanoparticles, leading to concentrated regions with strong interparticle interactions. These interactions resulted in a superspin glass-like behavior in all samples with transition temperatures located at 74 and 208 K.