Exchange Fe3+-Fe3+ interactions in ferrites with spinel structure

Abstract

3+ 3+-FeIt is known that intersublattice (A -B) exchange Fe interaction in many types of ferrites with spinel structure causes in the main the ferrimagnetic order.However, the presence, as a rule, of two (or more) types of magnetic ions in ferrites makes this important interaction difficult to study.The zinc and magnesium monoferrites belong to the not numerous class of compounds with one type of magnetic cations. But their magnetic properties in the equilibrium state essentially differ on account of the different cation distribution.Zinc ferrite has the structure of a normal spinel and therefore there exist in it weak negative iron-iron interactions in the B-sublattice that cause antiferromagnetic ordering of magnetic moments at low temperatures (1). OF the contrary, magnesium ferrite turns out to be a typical ferrimagnet due to a structure similar to the inversed ond (2).It is natural that ferrites of similar structure and with sufficient number of magnetoactive cations in A-and B-sublattices should be the most convenient ones for studying the intersublattice exchange Fe -Fe interactions. 3+ 3+As it was shown in (3) such isostructural (with equally probable distribution of cations over A-and B-sites) state in such class of ferrites might be achieved by the influence of fast neutrons upon them.The study of the suggested cation distribution and of the character of exchange interactions in irradiated zinc and magnesium ferrites has been carried out by the method of powder neutronography. The separation of nuclear and magnetic scatterings in the neutron diffraction pattern has been achieved with a magnetic field being applied along the scattering vector during the measuring process. The details of the experimental methods a r e given in (3).

Influence of cation disorder on the magnetic properties of ball-milled ilmenite (FeTiO3)

“…Part of the reason for this might be that the antiferromagnetic exchange coupling between nearest neighbor Fe 2þ in adjacent A and B layers is only on the order of À10 K and comparable in size to the in-plane ferromagnetic coupling (w10 K per Fe 2þ eFe 2þ interaction) [40], while for the ZnFe 2 O 4 [22,23,28] and Ni 0.5 Zn 0.5 Fe 2 O 4 [27] ferrites the induced antiferromagnetic coupling between A and B sites can be stronger (e.g. wÀ19 K [41] and as strong as wÀ45 K [42] per cation interaction). Moreover, it is possible that the cation-disordered distribution of Fe 2þ and Ti 4þ ions in ball-milled ilmenite leads to significant magnetic frustration, resulting in a reduced effective exchange coupling.…”

Structural and magnetic properties of zinc ferrite thin films irradiated by 90 keV neon ions

“…To justify the irradiation-induced magnetization, it can be assumed that atomic displacements of Fe 3+ cations at tetrahedral sites took place. Under irradiation, in a volume fraction of the samples, iron atoms undergo displacement from octahedral to tetrahedral sites of the spinel structure [53]. Implicitly, Zn 2+ cations can move from tetrahedral to octahedral sites.…”