Magnetic behavior of the oxide spinels: Li0.5Fe2.5−2x Al x Cr x O4

Abstract

In order to study the effect of substitution of Fe 3+ by Al 3+ and Cr 3+ in Li 0.5 Fe 2.5 O 4 on its structural and magnetic properties, the spinel system Li 0.5 Al x Cr x Fe 2.5−2x O 4 (x = 0.0, 0.2, 0.4, 0.5, 0.6 and 0.8) has been characterized by X-ray diffraction, high field magnetization, low field ac susceptibility and 57 Fe Mössbauer spectroscopy. Contrary to the earlier reports, about 50% of Al 3+ is found to occupy the tetrahedral sites. The system exhibits canted spin structure and a central paramagnetic doublet was found superimposed on magnetic sextet in the Mössbauer spectra (x > 0.5).

On the magnetic compensation effect of lithium‐chromium ferrites Li0.5CrxFe2.5–xO4 (0 ≤ x ≤ 1.55)

“…Ferrites are magnetic materials combining insulating and ferrimagnetic properties, and they have long been used in technology [1][2][3][4]. In the classical theory of ferrimagnets [5], Néel had predicted the unusual thermal variation of the spontaneous magnetization.…”

On the effect of thermal history on magnetic properties of CuFe2−2xAlxCrxO4 system

“…The introduction of Cr 3+ ions gives rise to strong B-B interaction [2]. There are reports on the magnetic properties of Al 3+ and Cr 3+ substituted for Fe 3+ in Ni-and Li-ferrites [3][4][5][6] and garnets [7]. The structural study on Al 3+ substituted Cu-ferrites [8] has shown the absence of tetragonal distortion for lower Al content and higher B-site occupancy of Al 3+ ions.…”

Mössbauer Study of ZnxCu1−xFe1.2Cr0.8O4

“…On the other hand, the percentage occupation of Fe 3þ ions at the B sites increases from 25% to 40%, while that of Cr 3þ ions at the B sites remains unchanged, thereby strengthening B-B interactions. This induces spin-canting in the octahedral (B) sites, thereby increasing the spin-canting angle with increasing Zn concentration [14,15]. The Nel temperature for each of the Zn x Cu 1Àx Fe 1:2 Cr 0:8 O 4 samples was determined by measuring the temperature at which the hyperfine pattern coalesces into a doublet.…”