Crystal and Magnetic Structure of the System Li_0.5+0.5xFe_2.5−1.5xTi_xO₄ (x=0.16, 0.44, and 0.72)

Abstract

The influence of thermal treatment on the structure of lithium titanium ferrite spinels of general formula Li(0.5+0.5x)Fe(2.5-1.5x)Ti(x)O4 (x=0.16, 0.44, and 0.72) has been studied by X-ray and neutron diffraction and analysed by the Rietveld method. The results allow us to conclude the presence of an ordered phase (space group P4(3)32) at room temperature for the sample with x=0.16; this phase does not appear for the remaining compositions. The magnetic properties evidence a ferrimagnetic ordering in the structures when a random cation distribution (space group Fd3 m) is obtained. An exhaustive study carried out by neutron diffraction measurements on these samples shows a different behaviour when the titanium content is increased, concluding that the lower substituted phase (x=0.16) exhibits a Neel's collinear ferrimagnetic structure, with the higher substituted structures being noncollinear (x=0.44 and 0.72).

Magnetic Behavior of the LiFeTiO4 Spinel

“…Nevertheless, for other samples of the system Li 0.5+0.5 x Fe 2.5- 1.5 x Ti x O 4 , the saturation is achieved from 2 to 50 kOe. This fact is characteristic of ferrimagnetic behavior . This AF component observed for LiFeTiO 4 can be attributed to the canting of magnetic ion moments in the sublattice as a consequence of the AF interactions between ions in the same sublattice.…”

“…Spinels of general formula Li 0.5+0.5 x Fe 2.5 - 1.5 x Ti x O 4 are of interest because they show order−disorder phase transitions that are mainly governed by composition and temperature. These structural transitions are also accompanied by noticeable variations in the magnetic behavior and this system has been widely studied. − In particular, the attention is focused on the high transition temperature from ferromagnetic to paramagnetic state that, in the parent phase, Li 0.5 Fe 2.5 O 4 , is as high as 958 K. − …”

“…During recent years, we have reported the structural characterization and magnetic behavior of some phases belonging to the system Li 0.5+0.5 x Fe 2.5 - 1.5 x Ti x O 4 . − Magnetic properties were interpreted on the basis of a Néel's collinear ferrimagnetic structure ( x = 0.16) that evolves to a noncollinear model for x = 0.44 and 0.72, and finally gives rise to a spin-glass behavior when the content of titanium is higher ( x = 1.28 and 1.50).…”

The effect on dielectric losses in lithium ferrite by cerium substitution

“…Substitution of non-magnetic ions Ce 3+ (1.034Å) in the vicinity of Fe 3+ (0.64Å) at octahedral B-site and a small amount of Li + (0.70Å) ions surrounding Fe 3+ at tetrahedral A-site. As a consequence, the Fe A O Fe B magnetic exchange interaction weakens may be responsible to reduce the saturation magnetization [8,9]. Frequency dependence of initial permeability (μ i ) is shown in Fig.…”