Disentangling the conductivity spectra of two-dimensional organic conductors

The optical spectrum of a κ -phase organic conductor is thoroughly analyzed for the example of κ -(BEDT-TTF) 2 Cu [ N(CN) 2 ] Br 0.85 Cl 0.15 in order to identify its various contributions. It is shown how the complex spectra can be decomposed using different approaches; the intradimer and interdimer contributions are discussed. In particular the fingerprints of electronic correlations in these spectra are considered

Charge-transfer processes in radical ion molecular conductors κ-(BEDT-TTF)2Cu[N(CN)2]Br x Cl1 − x : The superconductor (x = 0.9) and the conductor with the metal-insulator transition (x = 0)

Optical spectral investigations of low-dimensional organic molecular conductors κ-(BEDT-TTF)2Cu[N(CN)2]Br x Cl1 − x with x = 0.9 (the superconductor with T c = 11.3 K) and x = 0 (the metal with the metal-insulator transition at T < 50 K) are performed in the range 50–6000 cm−1 (6 meV–0.74 eV) at temperatures from 300 to 20 K. The optical conductivity spectra are quantitatively analyzed in terms of the proposed model, according to which the charge transfer involves two types of charge carriers, i.e., electrons (holes) localized on clusters (dimers and tetramers formed by BEDT-TTF molecules) and quasi-free charge carriers, with the use of the tetramer “cluster“ model based on the Hubbard Hamiltonian for correlated electrons and the Drude model for quasi-free charge carriers. Physical parameters of the model, such as the energy of Coulomb repulsion between two electrons (holes) in one molecule, the transfer integrals between molecules inside the dimer and between dimers, and the electron-molecular vibration coupling constants, are determined. The anisotropy of the spectra in the conducting plane is explained. The inference is made that only electrons localized on clusters couple with intramolecular vibrations

Structure and magnetic properties of LiNi1-xCoxPO4 magnetoelectrics with x = (0, 0.1, and 0.2)

We present the magnetic properties of LiNi1-xCoxPO4 magnetoelectrics, with x = (0-0.2), and their analysis of concentration dependences. Samples have been synthesized by a glycerol-nitrate method. To refine crystal structure X-ray diffraction measurements were carried out. Magnetic measurements were performed at the external magnetic field of 500 Oe over the temperature range (2-300) K. The neutron powder diffraction patterns of LiNi0.9Co0.1PO4 were recorded over temperature interval from 4.4 K up to 25 K. The partial doping in the LiNi1-xCoxPO4 magnetoelectrics the Ni ions for Co ions leads to a narrowing of the temperature interval where the incommensurate phase is established. © Published under licence by IOP Publishing Ltd.3.6121.2017/8.902.The work was supported by MES of RF (contract No. 3.6121.2017/8.9), and by Act 211 Government of RF (contract No. 02.A03.21.0006)

Magnetic properties of Sr2Ni1-xMgxMoO6 (x = 0.25 and 0.5) double perovskite structure

Sr2Ni1-xMgxMoO6 (x = 0.25 and 0.5) double perovskites were synthesized by pyrolysis of glycerol-salt mixtures and their magnetic properties were investigated. X-ray diffraction was employed to refine crystal structures of these perovskite materials and set sample purity degree. The magnetic ground state of Sr2Ni1-xMgxMoO6 (x = 0.25 and 0.5) has been characterized using magnetic susceptibility measurements. They indicate that Sr2Ni0.75Mg0.25MoO6 is ordered in an antiferromagnetic state below 56 K while Sr2Ni0.5Mg0.5MoO6 is paramagnetic. © Published under licence by IOP Publishing Ltd.3.6121.2017/8.9A03.21.0006, 02.The work was supported by MES of RF (contract No. 3.6121.2017/8.9), and by Act 211 Government of RF (contract No. 02.A03.21.0006), and supported in part y FASO of Russia (theme “Flux” No. AAA-A18-118020190112-8)

Structure and magnetoelectric coupling of LiNi1-xCoxPO4 multiferroics

This work was supported by MES of RF (contract No. 3.6121.2017/8.9), Act 211 Government of RF (contract No. 02.A03.21.0006), and supported in part by FASO of Russia (theme “Flux” No. AAA-A18-118020190112-8). The equipment of the Ural Center for Shared Use “Modern nanotechnology” SNSM UrFU was used