A. N. Vinogradov

Giant change in infrared light transmission in La0.67Ca0.33MnO3 film near the Curie temperature

Yu. P. Sukhorukov,, E. A. Gan’shina, B. I. Belevtsev, N. N. Loshkareva, A. N. Vinogradov, K. D. D. Rathnayaka, A. Parasiris, D. G. Naugle Institute of Metal Physics, Ural Division of the Russian Academy of Sciences, 620219 Ekaterinburg, Russia Physics Department, Moscow State University, 119899, Moscow, Russia B. Verkin Institute for Low Temperature Physics & Engineering, Ukrainian Academy of Sciences, Kharkov, 61103, Ukraine Department of Physics, Texas A&M University, College Station, TX 77843-4242, USATransport, magnetic, magneto-optical (Kerr effect) and optical (light absorption) properties have been studied in an oriented polycrystalline La0.67Ca0.33MnO3 film which shows colossal magnetoresistance. The correlations between these properties are presented. A giant change in infrared light transmission (more than a thousand-fold decrease) is observed on crossing the Curie temperature (about 270 K) from high to low temperature. Large changes in transmittance in a magnetic field were observed as well. The giant changes in transmittance and the large magnetotransmittance can be used for development of IR optoelectronic devices controlled by thermal and magnetic fields. Required material characteristics of doped manganites for these devices are discussed.

Effect of isovalent doping of manganite (La1−xPrx)0.7Ca0.3MnO3 films (0≤x≤1) on their optical, magnetooptical, and transport properties near the metal-insulator transition

The optical, magnetooptical, and electric properties of epitaxial (La1−xPrx)0.7Ca0.3MnO3 films (0≤x≤1) grown by MOCVD on LaAlO3 and SrTiO3 substrates were studied. It is shown that the decrease in the average cation radius resulting from isovalent substitution of the Pr for La ions brings about a lowering of the Curie temperature, the metal-insulator transition temperature, and the temperatures of the maxima in magnetotransmission (MT) and magnetoresistance (MR). These temperatures depend only weakly on the substrate type. Substitution of La by Pr does not change the shape of the spectral response of the transverse Kerr effect. For concentrations x≤0.50, the maximum values of the Kerr effect and of the MT vary insignificantly, which should be assigned to the existence of a singly connected ferromagnetic metallic region at low temperatures. In films with x=0.75, the presence of ferromagnetic metallic drops in an antiferromagnetic insulating matrix was revealed. The totality of the experimental data obtained suggest that nanoscopic magnetic and electronic nonuniformities exist both in films with a singly connected metallic region and in an x=1 film, which is an antiferromagnetic insulator.

The evolution of magneto-transport and magneto-optical properties of thin La0.8Ag0.1MnO3+δ films possessing the in-plane variant structure as a function of the film thickness

Epitaxial La 0.8 Ag 0.1 MnO 3+δ films of different thicknesses (500-1000 nm) were grown on ZrO 2 (Y 2 O 3 ) substrates. Their optical, magneto-optical and transport properties were studied in order to clarify the effect of the epitaxial variant structure and Ag ion distribution on the conductivity, magnetoresistance and infrared magnetotransmission in these films. An original method was developed for separating MR contributions related to the colossal magnetoresistance near T C and the tunnelling magnetoresistance. It was established that in the La 0.8 Ag 0.1 MnO 3+δ films spin-polarization of electrons P reached ∼0.5. The transverse Kerr effect revealed the irregular distribution of Ag ions through the film thickness. The comparison of optical and electrical data implies lower silver content near the film-substrate boundary in relation to that in the domain volume.

Evolution of the optical and magnetooptical properties of amorphous metal-insulator nanocomposites

Magnetic, optical, and magnetooptical (MO) properties of (Co45Fe45Zr10)x(SiO2)100−x and (Co41Fe39B20)x(SiO2)100−x granular nanocomposites of the amorphous ferromagnetic metal-insulator type were studied in a broad range of the magnetic component concentrations x. The MO response of nanocomposites increases in the vicinity of the percolation transition. Using the experimentally determined values of optical constants and the equatorial Kerr effect, the diagonal and nondiagonal components of the permittivity tensor of nanocomposites were calculated for the first time. The nondiagonal components of this tensor are nonlinear functions of x, the most pronounced variations being observed near the percolation threshold. Experimental data on the MO effect and the permittivity tensor were theoretically modeled within the framework of the effective medium approximation and the Maxwell-Garnett approximation. The most adequate description was obtained with the symmetrized Maxwell-Garnett approximation, which provides for a good (semiquantitative) agreement between theory and experiment under certain assumptions about the microstructure of nanocomposites.

Optical and magneto-optical properties of ferromagnetic La1 ? xBaxMnO3 single crystals

The optical and magneto-optical properties of ferromagnetic La(1-x)Ba(x)MnO(3) single crystals with x=0.15, 0.20 and 0.25 are studied. The components of the permittivity tensor are obtained by spectral ellipsometry techniques and transverse Kerr effect measurements. The Kerr effect spectra depend substantially on the Ba content. The plasma frequency is estimated. In the paramagnetic semiconductor state, the small polarons contribute to conductivity in La(0.85)Ba(0.15)MnO(3), in La(0.75)Ba(0.25)MnO(3) no evidence for polarons is found even in the semiconductor state. For La(0.85)Ba(0.15)MnO(3) (T(C)=214 K), the metallic phase is estimated to occupy less than 1% of the total volume at T=190 K. It is shown that in La(0.75)Ba(0.25)MnO(3), the energy gap vanishes and the metal-semiconductor transition occurs somewhat below T(C) rather than at T=T(C).

Evolution of magnetooptical and transport properties of La1−xAgxMnO3 films depending on silver concentration

Evolution of optical, magnetooptical, and transport properties of La1−xAgxMnO3/SrTiO3 epitaxial films depending on the silver concentration (x = 0.05, 0.10, 0.15, and 0.25) is studied. The highest values of the Curie temperature (TC ≈ 317 K), magnetoresistance (∼16%), magnetotransmission (∼8%), and transverse Kerr effect (δ ∼ 20 × 10−3) are attained for a concentration x = 0.10 of Ag+ ions. Comparison of the temperature dependences of the transmission of IR radiation, resistivity, magnetotransmission, magnetoresistance, and Kerr effect indicates electronic and magnetic inhomogeneity of the films in spite of saturation of films with silver. This feature of the film state is explained using the concepts of epitaxial stresses and metastable point defects.

Spin states and phase separation in La 1 − x Sr x CoO 3 ( x = 0.15 , 0.25 , 0.35 ) films: Optical, magneto-optical, and magnetotransport studies

Optical absorption and transverse Kerr effect spectra, resistivity, and magnetoresistance of

Sm0.55Sr0.45MnO3/Nd0.55Sr0.45 MnO3 heteroepitaxial structure: Optical and magnetotransport properties

{mathrm{La}}_{1ensuremath{-}x}{mathrm{Sr}}_{x}{mathrm{CoO}}_{3}(x=0.15,0.25,0.35)

Resonant enhancement of the transversal Kerr effect in the InMnAs layers

films have been studied. The temperature dependences of the optical and magneto-optical properties of the films exhibit features which can be attributed to the transition of the

Properties of Structures Based on Laser-Plasma Mn-Doped GaAs and Grown by MOC-Hydride Epitaxy

{mathrm{Co}}^{3+}