M. Pugaczowa-Michalska

Electronic structure and magnetism of Fe3−xCrxSi alloys

Abstract The study of the electronic structure and magnetic properties of the Fe3−xCrxSi compound is motivated by the Mossbauer and neutron spectroscopy measurements showing unusual behaviour of Cr in such alloys. The site preferences of Cr in Fe3Si and the effect of local environment on formation of local magnetic moments are examined using self-consistent spin-polarised TB-LMTO method. The results of calculations essentially confirm the values and orientations of magnetic moments of iron and chromium atoms. However, they do not explain an experimental observation of almost equal occupation of A, B and C sites by chromium.

Structure, hydrogen bond network and proton conductivity of new benzimidazole compounds with dicarboxylic acids

Dicarboxylic acids are interesting for crystal engineering due to their ability of hydrogen bond formation. To find a relationship between the molecular structure and the properties of proton conducting materials, we synthesized two compounds of benzimidazole with dicarboxylic acids of different chain length: glutaric and pimelic acids. The structure of the compounds was determined by X-ray diffraction and compared with molecular arrangement studied by 13C CP/MAS NMR spectroscopy supported by Density Functional Theory computations for benzimidazole. Benzimidazole was found to form salt with glutaric acid in a 1 : 1 ratio and monoclinic layer-type structure with P21/n space group. Flat layers, parallel to (−102) plane, are built of glutaric acid molecules linked into rectangular-type chains by O–H⋯O bonds and benzimidazole molecules attached to the chains by N–H⋯O bonds. The molecule of the benzimidazole compound with pimelic acid contains two benzimidazole rings and one pimelic acid chain. The structure with alternating layers, built of two groups of benzimidazole dimers and layers of pimelic acid chains, belongs to P21/n space group. The acid layers are built of pimelic acid molecules linked by O–H⋯O hydrogen bonds into chains parallel to [30−1] direction and the benzimidazole dimers are linked to the acid layers by N–H⋯O bonds. Impedance spectroscopy studies in wide frequency and temperature range of pellets made of powdered compounds enabled to separate the contributions of crystalline and grain boundary parts to the electric conductivity. The conductivity (averaged over all directions) of the crystalline compounds of benzimidazole with glutaric and pimelic acid is characterized by activation energy of 2.5 eV and 1.6 eV, respectively, which is in an agreement with the hydrogen bond network in the materials.

Electronic and Magnetic Properties of BiFeO3: Gd3+

The effect of the magnetically active Gd3+ substitution on the electronic structure and magnetic properties of Bi0.75Gd0.25FeO3in Pnma and Pn2 1 a structures is examined by using DFT method. Our calculations revealed that the Bi0.75Gd0.25FeO3has nonzero total magnetic moment, which arises from antiparallel spin moments on Fe sites and a reduced spin moment on Gd. The band gap of the insulating ground state is predicted to be at least of 2.05 eV.

Effect of local environment on the magnetic properties of the (Ni1-xCox)2MnSn alloy

Abstract The electronic structure and the ground-state properties of the quaternary Heusler alloy (Ni 1− x Co x ) 2 MnSn has been studied by the self-consistent TB-LMTO method. The ground-state properties are in good agreement with experimental data. In particular, the observed linear change of total magnetic moment with concentration x is reproduced by our calculations. We present the values of local magnetic moments of the Co and Ni atoms for various possible configurations. The dependence of magnetic moments on the local environment is studied in detail for all concentrations.

An Influence of the Local Environment on Local Magnetic Moments and Hyperfine Fields in Fe3-xMnxAl

Ferromagnetic, intermetallic compound Fe3Al exhibits DO3-type crystal structure. There are two non-equivalent types of iron with different chemical neighbourhood – (A,C) and B sublattices. As a consequence of the different nearest environments of the iron atoms at these sites the different electronic and magnetic properties connected with these positions are observed. The aim of our research is to investigate the influence of the local surrounding of the iron on its magnetic moment and hyperfine field in compound Fe3-xMnxAl where iron is substituted by manganese.

Effect of Co Substitution on Ni2MnGe Heusler Alloy: ab initio Study

Ab initio calculations shown that the Co substitution instead of Ni in Ni

Proton Conducting Compound of Benzimidazole with Sebacic Acid: Structure, Molecular Dynamics, and Proton Conductivity

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Electronic Structure and Magnetic Properties of Ni_2MnGa_{1-x}Ge_{x} and Disordered Ni_{2}MnSn Heusler Alloys

MnGe with the L2

Electronic and magnetic properties and their response to pressure in Ni2MnB

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An influence of the local environment on local magnetic moments and hyperfine fields in Fe3−xCrxSi

crystallographic structure leads to a decrease of the lattice constant and an increase of the total magnetic moment of the Ni