Investigation of the field-induced ferromagnetic phase transition in spin-polarized neutron matter: A lowest order constrained variational approach

Abstract

In this paper, the lowest order constrained variational (LOCV) method has been used to investigate the magnetic properties of spin polarized neutron matter in the presence of strong magnetic field at zero temperature employing AV 18 potential. Our results indicate that a ferromagnetic phase transition is induced by a strong magnetic field with strength greater than 10 18 G, leading to a partial spin polarization of the neutron matter. It is also shown that the equation of state of neutron matter in the presence of magnetic field is stiffer than the case in absence of magnetic field.

Anisotropic pressure in dense neutron matter under the presence of a strong magnetic field

“…A complete spin polarization in the magnetar core is not allowed by the appearance of the negative pressure along the direction of the magnetic field, contrary to the conclusion of Ref. [37] where the pressure anisotropy in a strong magnetic field was disregarded. Fig.…”

“…This effect was not considered in Ref. [37], thus, leaving the possibility of the formation of a fully polarized state of neutron spins in a strong magnetic field open. In the given study, we provide a fully self-consistent calculation of the thermodynamic quantities of spin polarized neutron matter taking into account the appearance of the pressure anisotropy in a strong magnetic field.…”

Finite temperature effects on anisotropic pressure and equation of state of dense neutron matter in an ultrastrong magnetic field

“…A complete spin polarization in the magnetar core is not allowed by the appearance of the negative pressure along the direction of the magnetic field, contrary to the conclusion of Ref. [38] where the pressure anisotropy in a strong magnetic field was disregarded. Fig.…”

“…Under such circumstances, if to admit the interior magnetic fields with the strength H > 10 18 G, a different scenario is possible in which a field-induced ferromagnetic phase transition of neutron spins occurs in the magnetar core. This idea was investigated in the recent article [38], where it was shown within the framework of a lowest constrained variational approach with the Argonne V 18 NN potential that a fully spin polarized state in neutron matter could be formed in the magnetic field H 10 19 G. Note, however, that, as was pointed out in Refs. [36,39], in such ultrastrong magnetic fields the breaking of the O(3) rotational symmetry by the magnetic field results in the anisotropy of the total pressure, having a smaller value parallel than perpendicular to the field direction.…”

“…This effect was not considered in Ref. [38], thus, leaving open the possibility of the formation of a fully polarized state of neutron spins in a strong magnetic field. The degree of spin polarization is an important issue for determining the neutrino cross sections in the matter, and, hence, it is relevant for the adequate description of the neutrino transport and thermal evolution of a neutron star [17].…”