nan Misbah-ul-Islam

Magnetic interactions in Cu-substituted manganese ferrites

Abstract A series of Mn1−xCuxFe2O4, with x=0, 0.25, 0.50, 0.75 and 1.0, spinel ferrites were prepared by standard ceramic method, to study the effect of compositional variation on magnetic susceptibility, saturation magnetization (Ms), Curie temperature (Tc) and magnetic moments (μB). The Curie temperatures have been evaluated by measuring the ac susceptibility using the mutual inductance technique. On increasing Cu contents from 0.0 to 0.50, the saturation magnetization increases while the Curie temperature decreases. On further increase in Cu contents, x>0.50 a decreasing trend in Ms is exhibited while Tc continues to decrease. This effect can be partially related to the low magnetic moments of Cu+2 ions. The dominant interaction in all ferrite samples is A–B interaction which is due to the negative values of the characteristic temperature θ(K) showing that the magnetic ordering is antiferromagnetic. The Y–K angle increases gradually with increasing copper contents and extrapolates to 90° for CuFe2O4. From the computation of Y–K angles for Mn1−xCuxFe2O4, it can be concluded that the mixed copper ferrites exhibit a non-collinearity of the Y–K type while MnFe2O4 shows a Neel type of ordering.

Cation distribution in Cu-substituted manganese ferrites

Abstract A series of spinel ferrites, i.e., Mn 1− x Cu x Fe 2 O 4 , with x =0, 0.25, 0.50, 0.75 and 1.0 were prepared by the standard ceramic method, aiming to study the relationship between structural parameters and concentration of the substituted copper ions. By determining the crystal structure, oxygen positional parameter and cation distribution through X-ray diffraction (XRD) and the R -factor method, it is revealed that these ferrites belong to the family of mixed or partially inverse spinels.

MAGNETIC PROPERTIES OF Cd-SUBSTITUTED COPPER FERRITES

Magnetism in Cu1-xCdxFe2O4 ferrites (x=0.0, 0.1, 0.2, 0.3, 0.4, 0.5) was measured using an ac susceptibility technique and the vibrating sample magnetometer. The orientation of spins at octahedral and tetrahedral sites and Y–K angles have been measured. For samples having x = 0.0, 0.1 and 0.2, the Y–K angle is measured to be zero and the samples follow Neels collinear model. For samples having x=0.2 a triangular spin arrangement on B-sites weaken the AB-interaction. Magnetic behaviour of these ferrite is predicted on the basis of the abovementioned observations.

The magnetic interaction in Zn-substituted manganese ferrites

Abstract The exchange integrals for Mn 1− x Zn x Fe 2 O 4 system for different concentrations of Zn ( x = 0.0, 0.05, 0.10, 0.15, 0.20) using magnetic susceptibility data for paramagnetic phase have been calculated whose values lies between 13.12 and 13.97 cm −1 . The data has been fitted with the expression for the magnetic susceptibility derived from the van Vleck formula by using the solution of spin Hamiltonian. The ground state was found to be ( S = 5 2 , S 13 = 5 2 ). The average value of J deduced from the experiment was used in the van Vleck expression. The magnetic susceptibility thus calculated is found to be in good agreement with its experimental value.

The effect of Cu substitution on the microstructure and magnetic properties of MnFe2O4 ferrite

The effect of compositional variation on grain size and porosity of Mn1 − xCuxFe2O4 ferrite, where x = 0.0, 0.25, 0.50, 0.75, 1.00, prepared by standard ceramic method are reported. From microstructure analysis it follows that porosity increases with the Cu concentration where as coercivity increases up to x = 0.50. Above x = 0.5 the decrease in coercivity is explained on the basis of Neels mathematical model treating the demagnetizing influence of non-magnetic material in cubic crystals. The coercivity, varies inversely with the grain size upto x = 0.5. The decrease in coercivity above x = 0.5 with grain size can be correlated with the inter-granular domain wall movement because of large porosity.