Elastic properties of superconducting MAX phases from first principles calculations

Using first-principles density functional calculations, a systematic study on the elastic properties for all known superconducting MAX phases (Nb2SC, Nb2SnC, Nb2AsC, Nb2InC, Mo2GaC and Ti2InC) was performed. As a result, the optimized lattice parameters, independent elastic constants, indicators of elastic anisotropy and brittle/ductile behavior as well as the so-called machinability indexis were calculated. We derived also bulk and shear moduli, Young's moduli, and Poisson's ratio for ideal polycrystalline MAX aggregates. The results obtained were discussed in comparison with available theoretical and experimental data and elastic parameters for other layered superconductors.Comment: 7 page

Study of transition temperatures in superconductors Final report, 11 Mar. 1968 - 10 Mar. 1970

Thermodynamic and electrical properties of niobium stannide and other superconductor

Coexistence of Long-Range Magnetic Order and Superconductivity from Campbell Penetration Depth Measurements

Application of a tunnel-diode resonator (TDR) technique for studies of the vortex response in magnetic superconductors is described. Operating at very small excitation fields and sufficiently high frequency, TDR was used to probe small-amplitude linear AC response in several types of single crystals where long-range magnetic order coexists with bulk superconductivity. Full local - moment ferromagnetism destroys superconductivity and can coexist with it only in a narrow temperature range ($\sim 0.3$ K). In contrast, weak ferromagnetic as well as antiferromagnetic orders can coexist with bulk superconductivity and may even lead to enhancements of vortex pinning. By analyzing the Campbell penetration depth we find sharp increase of the true critical current in the vicinity of the magnetic phase transitions. We conclude that critical magnetic fluctuations are responsible for this enhancement