Cationic exchange in nanosizedZnFe2O4spinel revealed by experimental and simulated near-edge absorption structure

Abstract

The non-equilibrium cation site occupancy in nanosized zinc ferrites (6-13 nm) with different degree of inversion (0.2 to 0.4) was investigated using Fe and Zn K-edge x-ray absorption spectroscopy XANES and EXAFS, and magnetic measurements. The very good agreement between experimental and ab-initio calculations on the Zn K-edge XANES region clearly show the large Zntransference that takes place in addition to the well-identified Fe 3+ [B]→Fe 3+ (A) one, without altering the long-range structural order. XANES spectra features as a function of the spinel inversion were shown to depend on the configuration of the ligand shells surrounding the absorbing atom. This XANES approach provides a direct way to sense cationic inversion in these spinel compounds. We also demonstrated that a mechanical crystallization takes place on nanocrystalline spinel that causes an increase of both grain and magnetic sizes and, simultaneously, generates a significant augment of the inversion.

Nanopartículas de ferrita MFe₂O₄ (M = Ni y Zn): síntesis hidrotermal y propiedades magnéticas

“…This temperature corresponding to the maximum is called blocking temperature (T B ) and above 20 K superparamagnetic behaviour is observed. It has been recently reported a progresive increase of T B with the inversion degree and the size of the particles (17). Both χ FC and χ ZFC are coincident above the T B .…”

Non-equilibrium cation influence on the Néel temperature in ZnFe2O4

“…Samples 2ZF4H and 2ZF10H were obtained after high energy ball milling (HEBM) 2ZF for 4 and 10 h [4]. Nanostructured ferrite (BZF10H) was obtained by HEBM bulk ZnFe2O4 for 10 h. The milling was carried out in a horizontal miller with a stainless steel vial and ball (mass to powder ratio of 10:1).…”

“…In any case, the AF configuration is driven by J BB superexchange interactions between Fe 3+ ions at octahedral B sites since the totality of diamagnetic Zn 2+ ions are preferentially located at tetrahedral A sites. Numerous works have reported that nanosized ZnFe 2 O 4 presents a non-equilibrium distribution of cations where Zn 2+ and Fe 3+ occupy both A and B sites [2][3][4]. This gives rise to J AB interactions that changes its long range ordering to a ferrimagnetic one with T N ∼ 460-490 K [3,5].…”

Preparation and microstructure of spinel zinc ferrite ZnFe2O4 by Co-precipitation method

“…The relationships between the microstructures and the synthesis conditions were discussed. The results show that the pure spinel zinc ferrites ZnFe 2 O 4 are formed when the Zn/Fe molar ratio is 1.05∶2 at pH＝8.5 or Zn/Fe molar ratio is 1∶2 at Ph＝9-10, and the precursors are sintered at 1100 Spinel zinc ferrite ZnFe 2 O 4 has attracted more attentions due to its interesting magnetic property and application in the photocatalysis [1][2][3][4][5][6][7][8] . Its magnetic property is mainly determined by its microstructure which is affected by the synthesis conditions and methods [9][10][11][12][13][14] .…”