Structural and magnetic properties of nickel antimony ferrospinels

Abstract

Spinel-type compounds of Fe-Ni-Sb-O system were synthesized as polycrystalline powders.The crystal and magnetic properties were investigated using X-ray and neutron powder diffraction, Mössbauer and X-ray absorption spectroscopy and magnetization measurements.The samples crystallize in the cubic system, space group Fd -3m. The distribution of cations between octahedral and tetrahedral sites was refined from the diffraction data sets using constraints imposed by the magnetic, Mössbauer and EDS results and the ionic radii. The cation distribution and the temperature dependence of the lattice parameter (a) and the oxygen positional parameter (u) were obtained. A chemical formula close to Fe 0.8 Ni 1.8 Sb 0.4 O 4 was determined, with Sb 5+ cations occupying octahedral sites, and Fe 3+ and Ni 2+ occupying both tetrahedral and octahedral sites. Fe 3+ mainly (85/15 ratio) occupy tetrahedral sites, and conversely Ni 2+ mainly reside on octahedral ones.The magnetic unit cell is the same as the crystallographic one, having identical symmetry relations. The results indicate that the compounds have a collinear ferrimagnetic structure with antiferromagnetic coupling between the tetrahedral (A) and octahedral (B) sites.Uniquely, the temperature dependence of the net magnetization of this rare earth free ferrimagnet exhibits a compensation point.

Rare-Earth Doped Gd3−xRExFe5O12 (RE = Y, Nd, Sm, and Dy) Garnet: Structural, Magnetic, Magnetocaloric, and DFT Study

“…The variation of the magnetic moment formula unit as a function of doping concentration, x, is shown in Figure 14 for four different RE 3+ ions mentioned above. When x = 0.0, i.e., in the Gd 3 Fe 5 O 12 sample, the µ B ~16 agrees with the previous calculations [41,61,62]. With the increase in the x value, the total magnetic moment increases in the case of Dy 3+ doping.…”

“…This discussion concludes that RE 3+ with a finite orbital angular momentum couple strongly with Fe 3+ sublattice moment via superexchange interaction. This behavior may be explained in terms of the temperature dependence of the magnetization of the three magnetic sublattices (dodecahedral, octahedral, and tetrahedral) balance each other [61,62]. Neel et al [41] reported that the magnetic properties of RE3Fe5O12 can be explained by assuming that the three sublattice ferrimagnetism is due to positive RE 3+ spin on dodecahedral sites, positive Fe 3+ spin on octahedral site, and negative Fe 3+ ion tetrahedral sites.…”