213 research outputs found
Infuence of pressure on magnetic phase transitions in the ferromagnetic superconductor UGe -- phenomenological approach
We propose a thermodynamic model of free energy expansion up to eighth order
of magnetisation to describe the complex magnetic phase transitions in
ferromagnetic superconductor UGe. The model successfully describes
transitions between ordered phases which take place without changing of
magnetic structure but only of magnetisation which is the case of UGe where
two magnetic phases with same structure but with different magnitude occur with
decreasing of temperature. We consider the infuence of pressure on magnetic
transitions in the simplest form of including it only in pressure dependence of
Curie temperature for the transition between the paramagnetic and themagnetic
phase with the lower magnetic moment FM1. Our results show that for pressures
lower than some limiting pressure the transition betweenlow-and
high-magnetisation phase remains of crossover type. Above this limiting
pressure this transition changes to real thermodynamic transition of first
order.Comment: 15 pages, 4 figures. arXiv admin note: text overlap with
arXiv:2108.0951
The existence of a stable noncollinear phase in a Heisenberg model with a complex structure
We have analyzed the properties of a noncollinear magnetic phase obtained in
the mean-field analysis of the model of two coupled Heisenberg subsystems. The
domain of its existence and stability is narrow and depends on the ratio
between the averaged over nearest neighbours microscopic exchange parameters.Comment: 7 pages, miktex, 3 figure
Phase transitions to spin-triplet ferromagnetic superconductivity in neutron stars
Effects of the anisotropy of Cooper pairs in spin-triplet ferromagnetic
superconductors are investigated on the basis of the Ginzburg-Landau theory. A
special attention is paid to the triggering of the superconducting state by the
ferromagnetic order. The ground states of these superconductors are outlined
and discussed. The idea about a possible coexistence of ferromagnetism and
spin-triplet superconductivity in neutron stars is introduced.Comment: 10 pages Latex2e, 2 figs, Proc. of the Leiden Workshop on Realistic
Models in Astrophysical Matter (AIP, N.Y., 2004
Phenomenological description of anisotropy effects in some ferromagnetic superconductors
We study phenomenologically by using the previously derived Landau free
energy, the role of anisotropy in ferromagnetic superconductors UGe2, URhGe,
and UCoGe. The three compounds are separately discussed with the special stress
on UGe2. The main effect comes from the strong uniaxial anisotropy of
magnetization while the anisotropy of Cooper pairs and crystal anisotropy only
slightly change the phase diagram in the vicinity of Curie temperature. The
limitations of this approach are also discussed.Comment: 12 pages, 4 figure
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