The infrared optical, magneto-optical properties of CoFe2O4 single crystals are considered. The magneto-absorption of natural light in the infrared spectral range in CoFe2O4 spinel is studied in the Voight experimental geometry. This magneto-optical effect is very high and associates with a change in the fundamental absorption edge and impurity absorption bands under a magnetic field. The magneto-absorption strongly depending on both the magnitude and the orientation of the magnetic field relative to the crystallographic axes of the crystal is presented in this paper. The contribution of magnetostriction to the magnetic anisotropy constant of the CoFe2O4 crystal is shown to be abnormally large. The clear connection between magneto-absorption of light in the infrared spectral range and magnetostriction of the CoFe2O4 spinel is established.
The process of electromagnetic field penetration through lead-doped lanthanum manganites exhibiting colossal magnetoresistance has been studied. The measurements have been performed in a range of radio frequencies from 20 kHz to 10 MHz in the temperature interval containing a magnetic phase transition. Application of a constant external magnetic field leads to an increase in the transmission coefficient. Relative variations of the electromagnetic field transmission coefficient are several times as large as the relative change in the dc magnetoresistance. The temperature dependence of the relative change in the transmission coefficient has been studied. Variations of the transmission coefficient sharply decrease in the vicinity of the phase transition temperature, but they still remain rather large at temperatures above the Curie point.
Absorption of centimeter waves in La0.6Y0.07Ba0.33MnO3 manganite powder is studied under the conditions of ferromagnetic resonance and antiresonance. It is found that interaction between different components of the microwave fields and the manganite distorts the shape of resonance lines and changes the resonance-to-antiresonance amplitude ratio. In the range of ferromagnetic resonance fields, great (up to 25 times) changes in the transmitted microwave power are observed.
Magnetic, magnetotransport and optical properties are experimentally studied. The mechanism of conduction is found to be different below and above the Curie temperature. This difference is explained by a shift of the mobility edge due to magnetic disorder.
The sequence of phase transitions in the system La2O3-MO(MCO3)Mn2O3, (M=Ca, Sr, Ba, Cd) and the span range of La1−xMxMnO3±δ solid solutions formed were studied. It is demonstrated that interaction begins at 650°C due to formation of divalent metal manganites. Just simultaneously as a result of oxidation-reduction processes and structural transformations the synthesis of small quantities of solid solutions takes place, which is kinetically favoured in the case of smaller divalent metal cations. The chemical transformation finishes at 1200°C. The values of x at all systems are near 0,35. The absence of CdMnO3 composition in the system CdO-MnO is proved.
Optical and magnetotransport properties are experimentally studied. It is found that mechanism of conduction is different below and above the Curie temperature. The difference is explained by shift of mobility edge because of magnetic disorder.