Magnetic properties of superparamagnetic lithium ferrite nanoparticles

Abstract

Magnetic properties of lithium ferrite nanoparticles of size in the range of 4–50nm, synthesized by a low-temperature method, have been evaluated. A broad maximum at ∼220K in the temperature variation of the zero-field-cooled magnetization as well as the ac susceptibility and divergence of the zero-field-cooled and field-cooled magnetizations below this temperature indicate the superparamagnetic behavior of the lithium ferrite particles of size ∼4nm. On the other hand, at high temperatures, these particles show a cusp immediately below the Curie temperature of bulk lithium ferrite (895K). This anomalous magnetic behavior of the lithium ferrite nanoparticles, similar to that arising from the Hopkinson effect for bulk materials, is probed in detail and is explained in terms of the cumulative effect of the temperature variation of the anisotropy and particle size growth during the measurements at high temperatures.

Magnetic and Mössbauer spectroscopic studies of NiZn ferrite nanoparticles synthesized by a combustion method

“…It is assumed that a magnetically dead layer is formed at the surface of the particles due to the uncompensated exchange interactions in a surface layer of thickness t. The thickness of this dead layer is related to c as c= 6t [18] from which the value of t is obtained as 0.96 nm. This value is comparable to the unit cell parameter of NiZn ferrite (0.84 nm) and also comparable to the values reported in the literature for different ferrites [18,19]. This indicates that at least one unit cell on the surface layer of the nanoparticles is magnetically inactive.…”

Lithium Ferrite: Synthesis, Structural Characterization and Electromagnetic Properties

“…This promotes the increase in the probability of the random distribution of magnetic moments and therefore an increase in the soft magnetic type response. In the literature [28,29], the magnetization of the lithium ferrite is around 60 emu/g, which is rather lower than the one obtained in this work (Figure 16). In these samples, the generation of the lithium ferrite phase takes to the decrease in the contribution of the α-Fe 2 O 3 particles with low magnetization.…”

Structural, magnetic and Mössbauer spectral studies of nanocrystalline Ni0.5Zn0.5Fe2O4 ferrite powders

“…It is therefore expected that the magnetic characteristics of the NiZn, Ni 0.5 Zn 0.5 Fe 2 O 4 ferrite particles synthesized by GNP will be strongly dependent upon the combustion reactions with varying ˚e. It is also expected that multipoint rapid decomposition of the complex with the simultaneous evolution of large amount of gases favors the formation of nearly monodispersed nanoparticles [19,20]. We demonstrate this aspect in the present investigation.…”

“…The mixture is stoichiometric when ˚e = 1, fuel-lean when ˚e > 1 and fuel-rich when ˚e < 1. This can allow a systematic variation of the particle size obtained by controlling the metal nitrate to glycine molar ratio [19]. With stoichiometric and fuel rich combustion mixtures, the GNP method is well known to give rise to inhomogeneous phases with submicron size particles.…”