Narrow Results

In this work we study the influence of the constant magnetic field up to 14 kOe to the temperature dependence of the electrical conductivity in the ab-plane of aluminium doped YBa₂Cu₃O_7-δ single crystals with an unidirectional twin boundaries system. The temperature dependence of the excess para-conductivity is interpreted within the Aslamazov–Larkin theoretical model of the fluctuation conductivity. It was shown that the lack of fan-shaped expansion of the resistive transitions in the magnetic field in these samples may be due to the lack of the non-pinning vortex liquid phase.

The influence of a high hydrostatic pressure on the basal-plane electrical resistance along the twin boundaries in underdoped HoBa₂Cu₃O${}_{7-\delta }$ single crystals is investigated. An enhancement of the phase segregation caused by the high-pressure-induced redistribution of the labile oxygen has been revealed. The temperature dependences of the electrical resistance above $T_c$ can be approximated well within the framework of the model of $s-d$ electron–phonon scattering.

The motion of individual twin boundaries in ferromagnetic Ni–Mn–Ga alloys is the basic mechanism by which large reversible strains are generated. The resulting mechanical response makes these alloys potential candidates for magneto-mechanical actuation applications. In this work, we characterize the relations between the magnetically induced strain response of Ni–Mn–Ga single crystals and their internal twin boundary arrangements and kinetics. The macroscopic response is measured under constant magnetic fields, while the kinetics of individual twin boundaries is measured by the pulsed magnetic field method. By testing two different crystals with different twinning microstructures, we show that the main characteristics of the macroscopic response can be controlled by the number of mobile twin boundaries. In addition, we show that the magnitudes of controlling kinetic parameters of different twin boundaries vary with their location within the sample.