Comparative studies on superconductivity in Cr₃Ru compounds with bcc and A15 structures

Abstract

Chromium (Cr) is a transition metal element with 3d orbital electrons. In most compounds containing Cr, due to the correlation effect, twofold features, namely localization and itinerancy are expected. The localization gives rise to a magnetic moment, while the latter exhibits as the effective coherent weight for conductivity. Here we report the physical properties of Cr3Ru compounds with bcc and A15 structures by using multiple experimental tools. The resistivity measurements show sharp superconducting transitions at Tc = 2.77 K and Tc = 3.37 K for the bcc and A15 structures, respectively. A high residual resistivity exists in both phases. Magnetization measurements also show rather narrow superconducting transitions, with a clear hump feature in the intermediate temperature region (about 150 K), which may be ascribed to the remaining antiferromagnetic spin fluctuations. A pronounced second peak effect has been observed in magnetization hysteresis loops in the superconducting state only for samples with bcc structure. The specific heat coefficient reveals a clear jump at Tc. We find that s-wave gaps can be adopted to fit the low temperature specific heat data of both samples yielding ratios of 2Δ/kBTc about 3.6, indicating a moderate pairing strength. Interestingly, the Wilson ratios RW = Aχ0/γn are 3.81 and 3.62 for the bcc and A15 phases, suggesting a moderate correlation effect of conducting electron in the normal state. Besides, for samples with A15 structure, another specific heat anomaly occurs at about 0.85 K and is sensitive to magnetic fields. In addition, by applying high pressures, both system will exhibit an enhancement of Tc with a rate of about 0.019 K/GPa and 0.013 K/GPa for the bcc and A15 phases, respectively. Our combinatory results point to unusual behavior of both superconducting and normal states in these two Cr based alloys.

First-Principles Study on Thermodynamic, Structural, Mechanical, Electronic, and Phonon Properties of tP16 Ru-Based Alloys

“…We note that the proposed tP16 X 3 Ru systems are relatively new; hence, their fundamental data are limited in the literature. In order to validate our model, we find that the calculated lattice constant of Cr 3 Ru is in accord with the experiment [33] and literature [21]. Similarly, our calculated lattice constants of the individual metals are in agreement with experimental data [34] (see Supplementary Materials (references [16,35,36] are cited in the Supplementary Materials)).…”

Record-High Superconducting Transition Temperature in a Ti1–xMnx Alloy with the Rich Magnetic Element Mn

“…We have performed a total of five runs of experiments to show the reproducibility of pressure-enhanced superconductivity in the Ti 1– x Mn x alloy, and the evolution of T c with pressure in different experiments is quite consistent with each other. Note that even though the superconductivity changes a lot under high pressures, the residual resistance ratio of Ti 1– x Mn x under high pressures is almost as small as it is at ambient pressure, which may be due to the scattering from disorders induced by the doping of magnetic elements. ,, …”

First-principles study of stability and electronic properties of B2 X–Ru alloys for high-temperature structural applications

“…While the Ru based transition metal alloys can possibly crystallize in various crystallographic phases including D0c, tP16, A15, B2, and L1 2, only their properties in the A15 [16,17,21], D0c [22] and tP16 [23,24], have been explored so far. Therefore, there is need to understand their behavior across all known stable phases to discover novel materials for high temperature structural applications.…”

“…While other structures were deemed unstable in this study, there is a possibility of stabilization through doping. This finding has led to numerous research efforts being directed towards the examination of Ru-based intermetallic alloys [14][15][16][17], particularly incorporating transition metal atoms. Utilization of transition metals is motivated by their capability to form alloys with relatively higher melting points and low densities [18] compared to main group metals [19].…”