The magnetization reversal in CoFe2O4/CoFe2 granular systems

Expanding the tunability and applicability of exchange-coupled/decoupled magnetic nanocomposites

“…Several studies report decoupling at RT in monoxide-containing samples 29,[45][46][47][48] Some decoupled ''monoxide-free'' examples are also found. [49][50][51][52][53] However, we consider it possible that the monoxide was overlooked in those works. The proximity in 2y of the monoxide and the spinel Bragg positions (see Fig.…”

Approaching Ferrite-Based Exchange-Coupled Nanocomposites as Permanent Magnets

“…Unfortunately, accomplishing an effective exchange-coupling between phases has proven more challenging in practice than in the theory. In the pursuit of a better understanding of the exchange-coupling phenomenon, a great amount of experimental and theoretical work has been dedicated to the subject during the past two decades, and it still remains an area of intensive research nowadays. − In particular, the CoFe 2 O 4 (hard)/Co–Fe alloy (soft) composite has been assiduously studied over the past few years. − Besides cobalt–iron alloys having the largest M s known at room temperature, the system has drawn special attention because it can be prepared by partial reduction of CoFe 2 O 4 . This chemical route directly leads to coexistence of the two magnetic phases, and consequently, a greater crystallographic coherency between them is expected compared with mixing independently synthesized species to make the composite.…”

“…The most extended strategy to prepare magnetic CoFe 2 O 4 /Co–Fe nanocomposites is a thermal treatment of CoFe 2 O 4 nanoparticles in a H 2 -rich atmosphere. − Other reduction agents have been used, e.g., activated charcoal or CaH 2 . These composites have also been made in the shape of dense ceramic materials by means of spark plasma sintering (SPS). , Regardless of the preparation method, monoxides, i.e., FeO or CoO, have often been detected as impurities in CoFe 2 O 4 /Co–Fe composites prepared through partial reduction. ,,, In none of the cases presented in the literature was it possible to determine whether the formation of this phase occurs during the reduction process (reaction intermediate) or at a later stage as a reoxidation triggered by the nanocomposites coming into contact with air.…”

A Nafion/polybenzimidazole composite membrane with consecutive proton-conducting pathways for aqueous redox flow batteries

“…21,35 As for the XRD patterns (Fig. 4b), the main diffraction peaks of the Nafion nanofibers and PBI matrix are present at 17.0 and 24.2°, respectively, 37,38 which are preserved in the NP-Fiber membrane. Moreover, the existence of the crystalline phase of the Nafion nanofibers further certifies that the Nafion nanofibers are not degraded by the PBI/DMAc solution during the membrane solidification.…”