Evidence of large exchange bias effect in single-phase spinel ferrite nanoparticles

Abstract

Sm3+ doped spinel cobalt ferrite nanoparticles with a generic formula CoSmxFe2−xO4 (x = 0.00, 0.06, 0.12 and 0.18) were prepared using wet chemical co-precipitation technique. The structural, optical, magnetic and dielectric characteristics of the samples were investigated carefully. The phase purity and growth of spinel cubic structure was verified by room temperature x-ray diffractograms. Mean crystallite size was observed within the range of 6 nm to 15 nm as calculated from Scherrer’s formula. A blue shift in the indirect optical band gap was noticed with increasing Sm percentage as observed in UV–vis spectra due to the nanosize effect. Superparamagnetic nature at 300 K was detected for all Sm doped ferrite samples. Field cooled (150 kOe) M-H loops obtained at 5 K revealed a large amount of exchange bias field (≈4 kOe) together with high coercivity for the sample having smallest sized particles. Dielectric responses of all samples showed that the hopping of electrons was the fundamental charge conduction mechanism and grain boundaries play a crucial role in determining the dielectric properties.

Introducing the magnetic properties in Fe doped ZnO nanoparticles for spintronics application

“…where is an absorption coefficient, represents an arbitrary constant, corresponds to the optical band gap and denotes an index which attains values of ½ for direct bandgap and 2 for indirect band gap semiconductor. The value of is calculated using this general formula [23,24] = and = log (8) where 'A' is absorbance and 't' indicates the thickness of materials. The absorption coefficient takes the form [24] = 2.303 (9) A graph between ( ℎ ) 2 versus ℎ was plotted to obtain the direct optical band gap of all samples which is well known as Tauc plot [23].…”

“…The value of is calculated using this general formula [23,24] = and = log (8) where 'A' is absorbance and 't' indicates the thickness of materials. The absorption coefficient takes the form [24] = 2.303 (9) A graph between ( ℎ ) 2 versus ℎ was plotted to obtain the direct optical band gap of all samples which is well known as Tauc plot [23]. Figure 6 depicts the magnetic hysteresis (M-H) curves registered at room temperature of all the samples.…”

“…The precipitate was dried in an open atmosphere and then ground into the fine powder [23]. All the synthesized samples were indexed as Fe-00, Fe-05, Fe-10 and Fe-15.…”

“…A graph between ( ℎ ) 2 versus ℎ was plotted to obtain the direct optical band gap of all samples which is well known as Tauc plot [23].…”

Tailoring the microstructural, magnetic and dielectric properties of vanadium ions substituted nickel ferrite nanocrystals

“…Other impotent factors that modify the magnetic properties of nanomaterials are dipole-dipole interactions, use of capping layer and texture of nano-objects. Also the existence of imperfections, defects and preparation method plays a crucial role in determining the magnetic properties of nanomaterials [9][10][11].…”