Effect of complex magnetic structure on the magnetocaloric and magneto-transport properties in GdCuSi

GdCuSi has been studied by structural, magnetic, magneto-thermal, and magneto-transport measurements. The compound crystallizes in the Ni2In-type hexagonal structure. Magnetic measurements show antiferromagnetic ordering at T (N) = 14.2 K and a magnetic anomaly near 5 K, which are confirmed by different measurements. Magnetocaloric effect (MCE) has been estimated from both magnetization and heat capacity data and it shows a change in sign below T (N). Similar to MCE, magnetoresistance (MR) data also show sign change below T (N). The compound shows large MCE and MR near its ordering temperature. The sign change in MCE and MR is attributed to the non-collinear antiferromagnetic structure of the compound. The theoretical calculations suggest competition of ferromagnetic and antiferromagnetic interactions, which causes non-collinear magnetic structure in this compound

Optical Properties and the Electronic Structure of Co2TiGe and Co2TiSn Heusler Alloys

The frequency dependences of the real part epsilon(1)(omega) and imaginary part epsilon(2)(omega) of the complex dielectric constant of the Heusler alloys Co2TiGe and Co2TiSn have been studied in the spectral range of 0.1-5 eV. It has been established that the interband electron transitions play a dominant role in the formation of the optical properties of these alloys. An anomalous behavior of the optical properties in the IR range of spectrum, namely, the absence of the Drude component of the optical conductivity sigma(omega), has been revealed. The results of the studies have been discussed based on the calculations of the electronic structure of the alloys

Magnetism in RRhGe (R = Tb, Dy, Er, Tm): An experimental and theoretical study

RRhGe (R = Tb, Dy, Er, Tm) compounds have been studied by different experimental probes and theoretical ab initio calculations. These compounds show very interesting magnetic and transport properties. All the compounds are antiferromagnetic with some of them showing spin-reorientation transition at low temperatures. The magnetocaloric effect estimated from magnetization data shows high values in all these compounds. Magnetoresistance is negative near the ordering temperatures and positive at low temperatures. The electronic structure calculations accounting for electronic correlations in the 4f rare-earth shell reveal the closeness of the antiferromagnetic ground state and other types of magnetic orderings in the rare-earth sublattice. These calculations are also in agreement with the experimental results. (C) 2015 Elsevier B.V. All rights reserved

Electronic structure of the TbMn0.33Ge2 compound: Band calculation and optical experiment

The results of the investigation of the electronic structure and optical properties of the TbMn0.33Ge2 compound have been presented. The spin-polarized calculations of the band spectrum have been performed within the framework of the local spin density approximation (LSDA) with a correction for strong correlations in the 4f shell of the rare-earth ion (the LSDA + U method). The optical constants have been measured using the ellipsometric method and a number of spectral and electronic characteristics of the compound under investigation have been determined over a wide range of wavelengths. The interband part of the experimental dependence of the optical conductivity has been interpreted using the results of the calculation of the electron density of states

Characterization of d and f Electronic States in RSn1.1Ge0.9 (R=Gd, Tb) Compounds by Optical Spectroscopy and Electronic-Structure Calculations

This paper presents the results of investigations of the electronic structure and optical properties of the GdSn1.1Ge0.9 and TbSn1.1Ge0.9 compounds. Employing the local spin density approximation accounting for strong electronic correlations in the 4f-shell of rare-earth ions, that is the LSDA+U method, we carry out the spin-polarized calculations of band structure. In a broad range of wavelengths the optical constants of the compounds are measured by an ellipsometry method. A number of spectral and electronic characteristics are calculated. Based on the calculated density of states the structural features of optical conductivity for the investigated intermetallic compounds are interpreted in the region of interband absorption

Electronic structure and optical spectroscopy of the GdRhGe compound

The optical properties of the GdRhGe compound have been investigated in a wide spectral range by ellipsometry. Self-consistent calculations of the electronic structure have been performed within the local electron spin density approximation with a correction to strong electron interactions in the 4f shell of gadolinium ions (LSDA+U method). The experimental dispersion relation of the optical conductivity in the region of interband light absorption is interpreted based on the results of calculating the electron densities of states

Theoretical and experimental investigations on the magnetic and related properties of RAgSn2 (R=Ho, Er) compounds

Polycrystalline RAgSn2 (R=Ho, Er) compounds, synthesized by arc melting method are found to crystallize in cubic crystal structure with the space group Pm3 m. The dc and ac magnetic susceptibility data show that the compounds are antiferromagnetic at low temperatures. The absence of magnetic hysteresis reveals the soft magnetic nature. Magnetocaloric effect has been estimated from magnetization data that show moderate value for these compounds. The structure of the electronic states and corresponding inter-band transitions calculated for these compounds within the LSDA+U method are found in good agreement with experimental optical conductivity. The theoretical calculations also confirm antiferromagnetic ordering in RAgSn2 (R=Ho, Er). The values of the effective magnetic moments of holmium and erbium are found to be close to the experimental ones

Ab Initio Simulation of the Electron Structure and Optical Spectroscopy of ErRhGe Compound

The results of investigation of the electronic structure and optical properties of ErRhGe are presented. The band spectrum of this compound is calculated in the local electron spin density approximation with correction for strong electron interactions in the 4f shell of the rare-earth metal (LSDA + U method) with allowance for the spin polarization. The optical constants of the compound are measured, and a number of spectral and electronic characteristics are determined by the ellipsometric method in a wide range of wave-lengths. Structural features of the optical conductivity spectrum in the interband absorption region are interpreted on the basis of the calculated electron state density

Electronic structure of RSn1.1Ge0.9 (R = Dy, Ho) ternary compounds: Band calculation and optical properties

The results of investigations of the electronic structure and optical properties of the compounds DySn1.1Ge0.9 and HoSn1.1Ge0.9 are presented. Our spin-polarized calculations of the electronic structure are carried out in the local spin density approximation with correction for strong electronic correlations (LSDA+U method) in the 4f shell of the rare-earth ion. In the wavelength range 0.22-15 mu m, the optical constants of the intermetallic compounds were measured by the ellipsometric method, and a number of spectral and electronic characteristics are determined. Based on the calculated densities of states, the structural features of the optical conductivity in the region of interband light absorption are interpreted

A comparative study of the optical properties of TbRhGe and DyRhGe

In this paper, experimental and theoretical optical properties of TbRhGe and DyRhGe have been reported and compared. Our measurements by the ellipsometric method in the wavelength range 0.22-15 mu m revealed significant differences in energy positions of the interband peaks in the spectral functions of these ternary compounds. The electronic structure of TbRhGe and DyRhGe calculated within the LSDA + U method was used to obtain theoretical optical conductivity, which is in good agreement with the experimental one. Further analysis allowed us to track changes in interband transitions related to the rare-earth 4f and rhodium 4d states, which are responsible for the observed differences in optical properties of TbRhGe and DyRhGe compounds. (C) 2015 Elsevier Masson SAS. All rights reserved