Peculiarities of the electronic transport in half-metallic Co-based Heusler alloys

Electrical, magnetic and galvanomagnetic properties of half-metallic Heusler alloys of Co$_2$YZ (Y = Ti, V, Cr, Mn, Fe, Ni, and Z = Al, Si, Ga, Ge, In, Sn, Sb) were studied in the temperature range 4.2--900 K and in magnetic fields of up to 100 kOe. It was found that varying Y in affects strongly the electric resistivity and its temperature dependence $\rho(T)$, while this effect is not observed upon changing Z. When Y is varied, extrema (maximum or minimum) are observed in $\rho(T)$ near the Curie temperature $T_C$. At $T < T_C$, the $\rho(T)$ behavior can be ascribed to a change in electronic energy spectrum near the Fermi level. The coefficients of the normal and anomalous Hall effect were determined. It was shown that the latter coefficient, $R_S$, is related to the residual resistivity $\rho_0$ by a power law $R_S \sim \rho_0^k/M_S$ with $M_S$ the spontaneous magnetization. The exponent $k$ was found to be 1.8 for Co$_2$FeZ alloys, which is typical for asymmetric scattering mechanisms, and 2.9 for Co$_2$YAl alloys, which indicates an additional contribution to the anomalous Hall effect. The temperature dependence of resistivity at low temperatures is analyzed and discussed in the framework of the two-magnon scattering theory.Comment: Invited Report on the Moscow International Symposium on Magnetism MISM-2017, pdf only, 6 pages, J. Magn. Magn. Mater., in pres

Peculiarities of the electronic and magnetic characteristics in Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) Heusler alloys close to the half-metallic ferromagnets and spin gapless semiconductors

The Hall Effect and magnetization of Heusler alloys Co2YSi (Y = Ti, V, Cr, Mn, Fe, Co, Ni) were measured at T = 4.2 K and 300 K in magnetic fields of up to 100 kOe as well as the temperature dependence of the electroresistivity from 4.2 to 300 K. The normal and anomalous Hall coefficients, saturation magnetization, residual resistivity, type and concentration of current carriers and their mobility were obtained. It was demonstrated that there is a clear correlation between the electronic and magnetic parameters obtained, depending on the number of valence electrons z, at the transition from Co2TiSi (z=26) to Co2NiSi (z=32). The observed peculiarities of electronic and magnetic parameters may be due to the appearance of the states of the half-metallic ferromagnet and/or spin gapless semiconductor. © Published under licence by IOP Publishing Ltd.This work was carried out as part of the state task of the Russian Ministry of Education and Science (themes “Spin”,No. AAAA-A18-118020290104-2) with partial support from the Russian Foundation for Basic Research (projects Nos. 18-32-00686 and 18-02-00739) and the Government of the Russian Federation (Act No. 211, contract No. 02.A03.21.0006)

Electrical and optical properties of a PtSn 4 single crystal

A topological semimetal PtSn4 single crystal was grown by method of crystallization from a solution in a melt. Then the electrical resistivity and galvanomagnetic properties (magnetoresistivity and the Hall effect) were studied in the temperature range from 4.2 to 80 K and in magnetic fields up to 100 kOe. The optical measurements were carried out at room temperature. The residual resistivity is shown to be low enough and amount to ∼ 0.5 μOhm•cm. The temperature dependence of the electrical resistivity has a metallic type, increasing monotonically with temperature. A sufficiently large magnetoresistance of 750% is observed. The majority carriers are supposed to be holes with a concentration of ∼ 6.8•10 21 cm -3 and mobility of ∼ 1950 cm 2 /Vs at T = 4.2 K as a result of the Hall effect studies. The optical properties of PtSn 4 have features characteristic of "bad" metals. © 2019 Published under licence by IOP Publishing Ltd.This work was partly supported by the state assignment of Russia (theme “Spin” No. АААА-А18-18020290104-2 and theme “Electron” No. АААА-А18-118020190098-5), by the RFBR (project No.17-52-52008) and by the Government of the Russian Federation (state contract No. 02.A03.21.0006)

Structure and magnetic properties of the Co2FeAl and Co2NiSi Heusler alloy films

The structural and magnetic properties (field dependences of the magnetization in magnetic fields of up to 6 kOe) of thin-film Co2FeAl, and Co2NiSi Heusler alloys grown by pulsed laser deposition on glass and a single-crystalline Al2O3 R-plane substrate at different growth temperatures (20, 280 and 420 °C) were studied. It was found that the stoichiometric composition of the films depends on the substrate temperature during growth and repeats the composition of the target for films grown at low temperatures. The films deposited on a single crystalline Al2O3 substrate have uniaxial magnetic anisotropy in the plane. © Published under licence by IOP Publishing Ltd.This work was partly supported by the state assignment of Minobrnauki of Russia (themes “Spin” No. АААА-А18-118020290104-2), RFBR grants (Nos. 18-32-00686 and 18-02-00739) and the Government of the Russian Federation (state contract No. 02.A03.21.0006)

Сравнительный анализ кишечной микробиоты при болезни Паркинсона и других неврологических заболеваниях

Currently the role of microbiota in diseases pathogenesis, its therapeutic and diagnostic potential are of the utmost interest for scientists and medical doctors. Parkinson’s disease is neurodegenerative disorder for which microbiota’s dysbiosis was previously shown.The main goal of the study is to compare the colon microbiota composition in case of Parkinson’s disease and other neurological pathologies, including idiopathic familial dystonia, essential tremor, multiple sclerosis, multiple system atrophy in order to determine the intestinal flora landscape specific to Parkinson’s disease.Material and methods. One hundred twenty-six patients, 93 with Parkinson’s disease and 33 with other neurological pathology were examined. For all patients, physical examination and fecal samples collection were performed. Microbiota taxonomic composition was analyzed by sequencing of bacterial 16S rRNA genes followed by bioinformatic and statistical analysis.As a result of the study, significant differences between groups in microbiota composition were found. Gut microbiota of patients with Parkinson’s disease was characterized by increase of Desulfovibrio piger, Lactobacillus mucosae, Yokenella regensburgei, Alistipes indistinctus, Oscillospira capillosus, Clostridium bolteae, Soleaferrea massiliensis, Butyricimonas virosa, Dorea massiliensis, Victivallis vadensis abundances. Patients with other neurological diseases had increased levels of bacteria belonging to Blautia, Intestinibacter, Coprococcus genera and Anoxystipes fissicatena, Fusobacterium periodonticum, Gemmiger formicilis, Papillibacter cinnamivorans, Roseburia faecis, Lachnoclostridium indolis, Clostridium populeti, Clostridium tertium, Roseburia intestinalis, Eubacterium desmolans, Eubacterium cylindroides, Clostridium clariflavum, Eubacterium eligens, Coprococcus eutactus, Intestinibacter bartlettii species in their gut microbiota.Consequently, gut microbiota in case of Parkinson’s disease was different from the microbiota of patients with other neurological diseases, including neuroinflammatory and neurodegenerative disorders, in terms of taxonomic diversity and composition. В настоящее время большой интерес представляет роль микробиоты в патогенезе различных болезней, а также ее диагностический и терапевтический потенциал. Болезнь Паркинсона – нейродегенеративное заболевание, для которого было показано изменение состава кишечной микробиоты в сравнении со здоровым контролем.Цель данного исследования – сравнительная характеристика кишечной микробиоты лиц с болезнью Паркинсона и другими неврологическими заболеваниями, включая идиопатическую семейную дистонию, эссенциальный тремор, рассеянный склероз, множественную системную атрофию для определения микробиотического ландшафта, характерного именно для болезни Паркинсона.Материал и методы. В исследование были включены 93 пациента с диагнозом болезни Паркинсона и 33 пациента с иными неврологическими заболеваниями. Для каждого пациента проведено физикальное обследование и собраны образцы фекалий. Определение состава микробиоты проводилась секвенированием бактериальных генов 16S рРНК с последующим биоинформатическим и статистическим анализом.Результаты. При сравнительном анализе состава микробиоты были найдены значимые различия. Микробиота кишечника лиц с болезнью Паркинсона характеризовалась увеличением содержания бактерий видов Desulfovibrio piger, Lactobacillus mucosae, Yokenella regensburgei, Alistipes indistinctus, Oscillospira capillosus, Clostridium bolteae, Soleaferrea massiliensis, Butyricimonas virosa, Dorea massiliensis, Victivallis vadensis. У лиц с другими неврологическими заболеваниями преобладали бактерии родов Blautia, Intestinibacter, Coprococcus и видов Anoxystipes fissicatena, Fusobacterium periodonticum, Gemmiger formicilis, Papillibacter cinnamivorans, Roseburia faecis, Lachnoclostridium indolis, Clostridium populeti, Clostridium tertium, Roseburia intestinalis, Eubacterium desmolans, Eubacterium cylindroides, Clostridium clariflavum, Eubacterium eligens, Coprococcus eutactus, Intestinibacter bartlettii.Выводы. Микробиота кишечника при болезни Паркинсона отличается по таксономическому разнообразию и бактериальному составу от микробиоты пациентов с другими неврологическими заболеваниями, в том числе нейровоспалительными и нейродегенеративными.

COMPARISON OF REACTOGENICITY AND IMMUNOGENICITY OF LIVE VACCINES AGAINST INFECTIOUS LARYNGOTRACHEITIS

Humoral immune response and ciliary activity of tracheal mucosa of poultry, vaccinated against infectious laryngotracheitis using ciliostatic test, was studied. Regardless of the vaccination route the vaccines decreased the ciliary activity by 5–9 % on Days 3 to 7 post vaccination. Herewith the vaccine ocular application in some chicks induced oneeye serous conjunctivitis, which resolved subsequently. Oral vaccination did not cause any clinical changes. Serological monitoring revealed an earlier and stronger immunity in poultry vaccinated by ocular route. The required seroprotection level in test groups was higher than the minimal value (80%) starting from Day 16 post vaccination. The period of immunity development after oral vaccination correlated with the vaccine dose volume. Moreover the domestic vaccine was highly competitive with foreign vaccines in immunogenicity and reactogenicity