194 research outputs found
Diamagnetic susceptibility of spin-triplet ferromagnetic superconductors
We calculate the diamagnetic susceptibility in zero external magnetic field
above the phase transition from ferromagnetic phase to phase of coexistence of
ferromagnetic order and unconventional superconductivity. For this aim we use
generalized Ginzburg-Landau free energy of unconventional ferromagnetic
superconductor with spin-triplet electron pairing. A possible application of
the result to some intermetallic compounds is briefly discussed.Comment: 7 pages, 1 figur
About the magnetic fluctuation effect on the phase transition to superconducting state in Al
The free energy and the order parameter profile near the phase transition to
the superconducting state in bulk Al samples are calculated within a
mean-field-like approximation. The results are compared with those for thin
films.Comment: 11 pages, miktex, 2 figure
Thermodynamics of ferromagnetic superconductors with spin-triplet electron pairing
We present a general thermodynamic theory that describes phases and phase
transitions of ferromagnetic superconductors with spin-triplet electron Cooper
pairing. The theory is based on extended Ginzburg-Landau expansion in powers of
superconducting and ferromagnetic order parameters. We propose a simple form
for the dependence of theory parameters on the pressure that allows correct
theoretical outline of the temperature-pressure phase diagram for which at low
temperatures a stable phase of coexistence of p-wave superconductivity and
itinerant ferromagnetism appears. We demonstrate that the theory is in an
agreement with the experimental data for some intermetallic compounds that are
experimentally proven to be itinerant ferromagnetic exhibiting spin-triplet
superconductivity. Some basic features of quantum phase transitions in such
systems are explained and clarified. We propose to group the spin-triplet
ferromagnetic superconductors in two different types of thermodynamic behavior,
on the basis of quantitative criterion deduced from the present theory and the
analysis of experimental data.Comment: Phys. Rev. B (2009) in PRESS; 14 pages, 1 table, 6 figures, Latex2
Meissner phases in spin-triplet ferromagnetic superconductors
We present new results for the properties of phases and phase transitions in
spin-triplet ferromagnetic superconductors. The superconductivity of the mixed
phase of coexistence of ferromagnetism and unconventional superconductivity is
triggered by the presence of spontaneous magnetization. The mixed phase is
stable but the other superconducting phases that usually exist in
unconventional superconductors are either unstable or for particular values of
the parameters of the theory some of them are metastable at relatively low
temperatures in a quite narrow domain of the phase diagram. Phase transitions
from the normal phase to the phase of coexistence is of first order while the
phase transition from the ferromagnetic phase to the coexistence phase can be
either of first or second order depending on the concrete substance. Cooper
pair and crystal anisotropies determine a more precise outline of the phase
diagram shape and reduce the degeneration of ground states of the system but
they do not change drastically phase stability domains and thermodynamic
properties of the respective phases. The results are discussed in view of
application to metallic ferromagnets as UGe2, ZrZn2, URhGe.Comment: 21 pages, 7 figures; Phys. Rev. B (2005) in pres
Honey bee genotypes and the environment
Although knowledge about honey bee geographic and genetic diversity has increased tremendously in recent decades (Meixner et al., 2013), the adaptation of honey bees to their local environment has not been well studied. The current demand for high economic performance of bee colonies with desirable behavioural characteristics contributes to changing the natural diversity via mass importations and an increasing practice of queen trade and colony movement. At the same time, there is also a growing movement in opposition to this trend, aimed at
conserving the natural heritage of local populations, with on-going projects in several countries (Strange et al., 2008; DallâOlio et al., 2008, De la RĂșa et al., 2009)
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