Enhanced magnetic performance in exchange-coupled CoFe₂O₄–LaFeO₃ nanocomposites

Abstract

Nanocomposite oxide system of (x)CoFe2O4 - (100-x)LaFeO3 with different weight percent of core-shell structured CoFe2O4 (x = 0,20,40,50,80,100) and LaFeO3 were fabricated, via a two-step sol-gel wet-chemical synthesis technique. The phase formation of the composites was confirmed by X-ray diffraction and the structural parameters of both the phases were attained from the Rietveld refinement results of XRD patterns. The elemental composition and microstructure of the resulting nanocomposites were examined by using energy-dispersive X-ray spectroscopy (EDX) and high-resolution transmission electron microscopy (HRTEM) technique, respectively. The detailed magnetometry studies at 300 K and 5 K reveal that the inter-and intra-phase magnetic interactions affect the saturation magnetization (MS), remanence magnetization (MR) and coercivity (HC) values of this bi-magnetic system. The remarkable feature of “pinched magnetic hysteresis loop” was evidenced in the [(50) CoFe2O4 - (50)LaFeO3] composite, leading to a lesser magnetic loss factor and better magnetic performance of this sample. The report depicts an improved interfacial exchange coupling at 5 K, for the nanocomposites of core-shell morphology and offers an understanding or explanation of improved magnetic performance for the (50)CoFe2O4 - (50)LaFeO3 nanocomposite and opens up an important way to design new multiferroic applications in low magnetic fields.

Crystal Structure and Bond-Valence Investigation of Nitrogen-Stabilized LiAl5O8 Spinels

“…Although the powder XRD (PXRD) or synchrotron XRD techniques can well outline the framework of the lattice, the diffraction data for Li ions is usually low intensity or indistinguishable, which brings about notable difficulties in refining the crystal structure by the Rietveld method, and the local crystal structure of cations could be hardly specified so far. , In the disordered oxynitride spinel, such as AlON, MgAlON, and so forth, the oxygen and nitrogen co-enter the anion site (32 e ) and form a face-centered-cubic close-packed arrangement, where the cations occupy the 8 a and 16 d sites. ,, Based on the constant anion model of γ-AlON, the first-principles calculation indicated that the N atoms in 32 e sites would distribute far away from each other and the Al vacancies in 16 d sites coordinate only with O atoms in the γ-AlON . These structural characters are also applicable to the Li y Al (16+ x – y )/3 O 8– x N x spinel.…”