Observation of subkelvin superconductivity in Cd₃As₂ thin films

We report an experimental observation of superconductivity in Cd3As2 thin films without application of external pressure. The films under study were synthesized by magnetron sputtering. Surface studies suggest that the observed transport characteristics are related to the polycrystalline continuous part of the investigated films with a homogeneous distribution of elements and the Cd-to-As ratio close to stoichiometric Cd3As

Control of Mooij correlations at the nanoscale in the disordered metallic Ta - nanoisland FeNi multilayers

Localisation phenomena in highly disordered metals close to the extreme conditions determined by the Mott-Ioffe-Regel (MIR) limit when the electron mean free path is approximately equal to the interatomic distance is a challenging problem. Here, to shed light on these localisation phenomena, we studied the dc transport and optical conductivity properties of nanoscaled multilayered films composed of disordered metallic Ta and magnetic FeNi nanoisland layers, where ferromagnetic FeNi nanoislands have giant magnetic moments of 10^3-10^5 Bohr magnetons (\mu_B). In these multilayered structures, FeNi nanoisland giant magnetic moments are interacting due to the indirect exchange forces acting via the Ta electron subsystem. We discovered that the localisation phenomena in the disordered Ta layer lead to a decrease in the Drude contribution of free charge carriers and the appearance of the low-energy electronic excitations in the 1-2 eV spectral range characteristic of electronic correlations, which may accompany the formation of electronic inhomogeneities. From the consistent results of the dc transport and optical studies we found that with an increase in the FeNi layer thickness across the percolation threshold evolution from the superferromagnetic to ferromagnetic behaviour within the FeNi layer leads to the delocalisation of Ta electrons from the associated localised electronic states. On the contrary, we discovered that when the FeNi layer is discontinuous and represented by randomly distributed superparamagnetic FeNi nanoislands, the Ta layer normalized dc conductivity falls down below the MIR limit by about 60%. The discovered effect leading to the dc conductivity fall below the MIR limit can be associated with non-ergodicity and purely quantum (many-body) localisation phenomena, which need to be challenged further.Comment: 29 pages, 8 figures. This is a post-peer-review, precopyedit version of an article published in Scientific Reports. The final authenticated version is available online at http://dx.doi.org/10.1038/s41598-020-78185-

Синтез и магнетосопротивление кристаллов (Cd1−x Znx)3As2 (x = 0,007)

The vapor phase growth of Cd3As2—Zn3As2 (in the following (Cd1−x Znx)3As2 solid solutions process is described. The (Cd0,993 Zn0,007)3As2 solid solution single crystals were synthesized. Scanning electron microscopy and electron diffraction data suggest high crystalline quality of studied sample. Its structure and surface morphology, indicating the presence of growth nuclei and cleavage planes, were investigated. Giant anisotropic magnetoresistance and Shubnikov — de Haas oscillations were observed at low temperatures. Obtained results suggests that peculiarities of Dirac semimetal phase persist in (Cd1−x Znx)3As2 solid solution at low zinc content. At the same time, there are indications of some differences with initial Cd3As2 properties.Описана процедура синтеза твердых растворов Cd3As2—Zn3As2 (в дальнейшем, (Cd1−x Znx)3As2 из паровой фазы. Синтезированы монокристаллы твердого раствора (Cd0,993 Zn0,007)3As2. Результаты сканирующей электронной микроскопии и дифракции электронов свидетельствуют о высоком кристаллическом совершенстве изученного образца. Исследована его структура и морфология поверхности, содержащей ростовые зародыши и плоскости скола. В области низких температур выявлены гигантское анизотропное магнетосопротивление, а также осцилляции Шубникова—де Гааза. Полученные результаты указывают на сохранение особенностей фазы дираковского полуметалла для твердого раствора (Cd1−x Znx)3As2 с низким содержанием цинка. В то же время присутствуют указания на возможные отличия от свойств исходного материала Cd3As2

Vapor-phase synthesis and magnetoresistance of (Cd₀.₉₉₃Zn₀.₀₀₇)₃As₂ single crystals

We report a highly anisotropic magnetoresistance of (Cd₀.₉₉₃Zn₀.₀₀₇)₃As₂ single crystals, which have been synthesized by the vapor-phase growth. Scanning electron microscopy and electron diffraction data confirm the high crystalline quality of obtained samples. Studied samples exhibit specific features such as octahedral nuclei growth and step-like morphology of the surface formed by {112} plane

High-temperature magnetism and microstructure of a semiconducting ferromagnetic (GaSb)1−x(MnSb)x alloy

We have studied the properties of relatively thick (about 120 nm) magnetic composite films grown by pulsed laser deposition using the eutectic compound (GaSb)0.59(MnSb)0.41 as target for sputtering. For the studied films we have observed ferromagnetism and an anomalous Hall effect above room temperature, confirming the presence of spin-polarized carriers. Electron microscopy, atomic and magnetic force microscopy results suggest that the films under study have a homogenous columnar structure in the bulk while MnSb inclusions accumulate near the surface. This is in good agreement with the high mobility values of charge carriers. Based on our data we conclude that the magnetic and magnetotransport properties of the films at room temperature are defined by the MnSb inclusions