V. D. Bessonov

Giant magnetorefractive effect in La0.7Ca0.3MnO3 films

Complex experimental investigations of the structural, optical, and magneto-optical properties (magnetotransmission, magnetoreflection, and transversal Kerr effect, as well as the magnetoresistance, of La0.7Ca0.3MnO3 epitaxial films indicate that magnetoreflection and magnetotransmission in manganite films can reach giant values and depend strongly on the magnetic and charge homogeneity of the films, their thickness, and spectral range under investigation. It has been shown that the optical enhancement of the magnetorefractive effect occurs in thin films as compared to manganite crystals. In the region of the minimum of the reflectance near the first phonon band, the resonance-like magnetorefractive effect has been observed, which is accompanied by change of the sign of the magnetoreflection. A model based on the theory of the magnetorefractive effect has been proposed to qualitatively explain this behavior.

Giant magnetorefractive effect in La{sub 0.7}Ca{sub 0.3}MnO{sub 3} films

Complex experimental investigations of the structural, optical, and magneto-optical properties (magnetotransmission, magnetoreflection, and transversal Kerr effect, as well as the magnetoresistance, of La0.7Ca0.3MnO3 epitaxial films indicate that magnetoreflection and magnetotransmission in manganite films can reach giant values and depend strongly on the magnetic and charge homogeneity of the films, their thickness, and spectral range under investigation. It has been shown that the optical enhancement of the magnetorefractive effect occurs in thin films as compared to manganite crystals. In the region of the minimum of the reflectance near the first phonon band, the resonance-like magnetorefractive effect has been observed, which is accompanied by change of the sign of the magnetoreflection. A model based on the theory of the magnetorefractive effect has been proposed to qualitatively explain this behavior.

Magnetorefractive effect in manganites with a colossal magnetoresistance in the visible spectral region

The magnetotransmission, magnetoreflection, and magnetoresistance of the La0.7Ca0.3MnO3 and La0.9Ag0.1MnO3 epitaxial films have been investigated. It has been found that the films exhibit a significant magnetorefractive effect in the case of reflection and transmission of light in the fundamental absorption region both in the vicinity of the Curie temperature and at low temperatures. It has been shown that the magnetorefractive effect in the infrared spectral region of the manganites is determined by a high-frequency response to magnetoresistance, whereas the magnetorefractive effect in the visible spectral region of these materials is associated with a change in the electronic structure in response to a magnetic field, which, in turn, leads to a change in the electron density of states, the probability of interband optical transitions, and the shift of light absorption bands. The obtained values of the magnetotransmittance and magnetoreflectance in the visible spectral region are less than those observed in the infrared region of the spectrum, but they are several times greater than the linear magneto-optical effects. As a result, the magnetorefractive effect, which is a nongyrotropic phenomenon, makes it possible to avoid the use of light analyzers and polarizers in optical circuits.

Magnetoreflection and Magnetostriction in Ferrimagnetic Spinels CoFe2O4

It is shown that magnetoreflectance of natural light up to +4% exists in magnetostrictive ferrimagnetic spinel CoFe2O4 single crystal; this effect is associated with a change of the fundamental absorption edge, the impurity absorption band, and the phonon spectrum under the action of a magnetic field. The correlation between the field dependences of magnetoreflectance and magnetostriction has been established. The physical mechanisms responsible for the spectral and field peculiarities of magnetoreflection have been explained. It is shown that the magnetorefractive effect in CoFe2O4, which is associated with magnetoelastic properties of the spinel, amounts to +1.5 × 10–3 in magnetic fields exceeding the saturation field. Analysis of magnetooptical and magnetoelastic data has made it possible to estimate deformation potential as Ξu = 20 eV for the valence band of the spinel.

Strain-magneto-optics of a magnetostrictive ferrimagnetic CoFe2O4

Abstract Significant magnetoreflection of unpolarized light in magnetostrictive ferrimagnetic single crystal of CoFe 2 O 4 has been revealed in the infrared spectral range. The magnetoreflection effect in CoFe 2 O 4 is up to 4% in a relatively small magnetic field. We experimentally demonstrate clear correlation between magnetostriction and magnetoreflection of light in CoFe 2 O 4 ferrite. The influence of a magnetic field on specular reflection is likely to be indirect: application of a magnetic field results in strong strains and deformations of the crystal lattice, which lead to the change in electron energy structure and hence reflection spectrum of CoFe 2 O 4 crystal - strain-magneto-optics.

Magnetoreflection of light in CoFe2O4 magnetostrictive spinel

The reflection and magnetoreflection of natural light within the infrared spectral range is studied in single crystals of CoFe2O4 ferrimagnetic ferrite spinel. Correlation between the reflection of light and magnetoelastic characteristics of this spinel is found. It is shown that the most significant magnetic-field-induced changes in the magnetoreflection of the spinel occur near the fundamental absorption edge and within the range of the phonon spectrum.

Magnetoreflection and magnetotransmission of light in manganites with CMR

The influence of a magnetic field on the reflection and transmission spectra of natural light is studied in the visible and infrared ranges of the spectrum in films and single crystals of manganite La0.7Ca0.3MnO3 with colossal magnetoresistance. The magnetoreflection and magnetotransmission effects are analyzed using the magnetorefractive approach developed for manganites.

Magnetotransmission in a Magnetostrictive CoFe 2 O 4 Crystal in the Faraday Geometry

It is shown that the magnetotransmission of unpolarized infrared radiation in the magnetostrictive crystal of CoFe2O4 ferrite spinel in the Faraday geometry can be as high as 30% at a magnetic field of 7.5 kOe. This effect is related to the field-induced shift of the fundamental absorption edge, as well as to changes in the intensity and positions of the impurity absorption bands. Correlation between the magnetic field dependence of magnetotransmission and magnetostriction is revealed. The contribution of the Faraday effect to the magnetotransmission is estimated. The analysis of magneto-optical and magnetoelastic characteristics taking into account the contribution of the deformation potential for the valence band is performed.

Infrared magnetoreflection in CoFe2O4single crystals

Magnetoreflection of unpolarized infrared radiation for single crystals of magnetostrictive cobalt ferrite spinel was studied. The correlation between magnetoreflection and magnetoelastic properties of that type of spinel was observed. It is shown that the magnetoreflection is the most pronounced in the region of a middle-infrared impurity band and reflection minima near phonon bands.

Magnetorefractive Effect in Doped La1-xKxMnO3 Thin Films

Influence the deposition of La3+ ions by monovalent K+ ions on magnetorefractive effect on magnetoreflaction and magnetotransmission modes in the infrared range for La1-xKxMnO3 epitaxial thin-films (х=0.05, 0.10, 0.15 и 0.18) has been studied. It has been shown that the magnetorefractive effect, transversal Kerr effect and magnetoresistance reach the maximum in optimally doped films at highest Curie temperature. The good agreement between calculated in framework of magnetorefractive effect theory and experimental data takes place only for optimally doped films, with potassium concentrations of 15 % and 18 %. At the other doping levels the films become charge and magnetic inhomogeneous. Magnetic and charge homogeneity influence strongly on magnetooptical effects in films. The resonance-like lines in magnetoreflection spectra of films are connected with the shifting of reflection minimum before the phonon bands under a magnetic field has been observed.