Low Field Microwave Absorption in Nanostructured Ferrite Ceramics Consolidated by Spark Plasma Sintering
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The low field microwave absorption (LFMA at 9.5 GHz) properties of clusters of Zn0.5Ni0.5Fe2O4 ferrite nanoparticles (NPs) consolidated by spark plasma sintering (PSP at temperatures in the 350–500 °C range) are analyzed. LFMA measurements were carried out at 77 and 300 K. The clusters, formed by ∼6 nm NPs, were first obtained by the forced hydrolysis in a polyol method from the corresponding metal acetates. It is found that the sign of LFMA, associated with the spin arrangement in the ferrite depends on the degree of consolidation. For monodispersed NPs, no change of sign is observed at low temperatures. For the as-produced clusters and the consolidated samples, a progressive change in the sign of the signal is observed as the sintering temperature is increased. This change of sign is associated with the occurrence of the triangular or canted Yafet–Kittel spin arrangement.
KeywordsMicrowave absorption Ferromagnetic resonance Magnetic nanoparticles Ferrites
Authors thank A. Alvarez (IPN, Mexico) for microwave measurements. This work was partially supported by ANR (France)-CONACyT (Mexico) grant # 139292.