In this paper, we calculate some of the polarized neutron matter properties, using the lowest order constrained variational method with the AV 18 potential and * Corresponding author † E-mail : bordbar@physics.susc.ac.ir ‡ Permanent address 1 employing a microscopic point of view. A comparison is also made between our results and those of other many-body techniques. 21.65.+f, 26.60.+c, 64.70.-p IntroductionPulsars are rapidly rotating neutron stars with strong surface magnetic fields in the range of 10 12 − 10 13 Gauss [1, 2, 3]. The physical origin of this magnetic field remains an open problem and there is still no general consensus regarding the mechanism to generate such strong magnetic fields in a neutron star. There exist several possibilities of the generation of the magnetic field in a neutron star, from the nuclear physics point of view, however, one of the most interesting and stimulating mechanisms which have been suggested is the possible existence of a phase transition to a ferromagnetic state at densities corresponding to the theoretically stable neutron stars and, therefore, of a ferromagnetic core in the liquid interior of such compact objects. Such a possibility has been studied by several authors using different theoretical approaches , but the results are still contradictory.Whereas some calculations, like for instance the ones based on Skyrmelike interactions predict the transition to occur at densities in the range (1 − 4)ρ 0 (ρ 0 = 0.16f m −3 ), others, like recent Monte Carlo [20] and Brueckner-Hartree-Fock calculations [21-23] using modern two-and three-body realistic interactions exclude such a transition, at least up to densities around five times ρ 0 . This transition could have important consequences for the evolution of a protoneutron star, in particular for the spin correlations in the medium which do

In this paper, we calculate properties of the spin polarized asymmetrical nuclear matter and neutron star matter, using the lowest order constrained variational (LOCV) method with the AV 18 , Reid93, U V 14 and AV 14 potentials. According to our results, the spontaneous phase transition to a ferromagnetic state in the asymmetrical nuclear matter as well as neutron star matter do not occur.

In this paper we study the magnetic susceptibility and other thermodynamic properties of the polarized nuclear matter at finite temperature using the lowest order constrained variational (LOCV) method employing the AV 18 potential. Our results show a monotonic behavior for the magnetic susceptibility which indicates that the spontaneous transition to the ferromagnetic phase does not occur for this system. *