In the present work, the effect of Dy3+ substitution on the structural and magnetic properties of CoFe2-xDyxO4 (x = 0.00 to 0.1 in step of 0.025) system synthesized by solution combustion method were investigated. The thermal decomposition process was investigated by means of differential and thermal gravimetric analysis that showed that the precursor could yield the final product after calcination above 600 °C. The phase purity and crystal lattice symmetry were estimated from X-ray diffraction studies. The microstructural features were observed by scanning electron microscopy that demonstrates the fine clustered particles with an increase of average grain size with Dy3+ content. The existence of constituent’s, i.e., Co, Fe, and Dy were authenticated by energy dispersive X-ray analysis. An infrared spectroscopy study shows the presence of two absorption bands in the frequency range around 590 cm−1 (ν1) and around 480 cm−1 (ν2); which indicate the presence of tetrahedral and octahedral group complexes, respectively, within the spinel lattice. Room temperature magnetization measurements showed that the saturation magnetization and hysteresis losses (coercivity) decreases with Dy3+ addition, which implies that these materials may be applicable for magnetic data storage and recording media.
Co1.2−xMnxFe1.8O4 (0≤x≤0.4)
compositions were synthesized by the autocombustion route by keeping the oxidizer to fuel ratio (Φe) at
1. Thermogravimetric analysis (TGA) shows the stable phase formation takes place at a temperature
above 600 °C. Structural characterization of all the samples was carried out by the x-ray diffraction
technique. Room temperature magnetization measurements showed that, for the
substitution of Co by Mn, there is an initial increase in the saturation magnetization (Ms) for lower
concentrations (i.e. x = 0.1
and 0.2); and then the magnetization decreases for higher concentrations (i.e.
x = 0.3
and 0.4). Also, it is observed that the coercivity
(Hc)
goes on decreasing with the substitution of Mn content, except for
x = 0.3
which shows a slight increase in coercivity as compared to
x = 0.4. Room temperature dielectric properties, namely relative dielectric permittivity (ε′), dielectric
loss (tanδ) and ac
conductivity (σac), for all the samples were studied as a function of applied frequency in the range from
20 Hz to 1 MHz. These studies indicate that the relative dielectric permittivity goes on
increasing with the increase of Mn content in Co ferrite and also all the samples show the
usual dielectric dispersion which is due to the Maxwell–Wagner-type interfacial
polarization. The ac conductivity measurement suggests that the conduction is due to small
polaron hopping.
Here we review the current status of magnetoelectric (ME) multiferroics and ME composite thin/thick films. The magnitude of ME coupling in the composite systems is dependent upon the elastic coupling occurring at the interface of piezoelectric and magnetostrictive phases. The multiferroic ME films in comparison with bulk ME composites have some unique advantages and show higher magnitude of ME response. In ME composite films, thickness of the films is one of the important factors to have enough signal. However, most of all reported ME nanocomposite structured films in literature are limited in overall thickness which might be related to interface strain resulting from difference in thermal expansion mismatch between individual phases and the substrate. We introduced noble ME composite film fabrication technique, aerosol deposition (AD) to overcome these problems. The success in AD fabrication and characterization of ME composite films with various microstructure such as 3-2, 2-2 connectivity are discussed.
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