Order parameter for the Ising ferromagnet

Joel L. Lebowitz

C. Gruber, Joel L. Lebowitz

Amir Hajibabaei, Farhad Shahbazi

In this paper, using high order perturbative series expansion method, the critical exponents of the order parameter and susceptibility in transition from ferromagnetic to disordered phases for 1D quantum Ising model in transverse field, with ferromagnetic nearest neighbor and anti-ferromagnetic next to nearest neighbor interactions, are calculated. It is found that for small value of the frustrating second neighbor coupling ( k<0.4 ), the exponents are the same as those of the classical 2D Ising model (B=1/8 and Y=7/8), but a deviation from 2D classical Ising universality class is observed for larger values of frustration (0.4< K<0.5). The reason for this deviation is the “disorder line” which becomes tangent to the Ferromagnetic phase boundary line at K=0.5

B G S Doman

Aycan Özkan, Bülent Kutlu

The fcc spin-1 Ising (BEG) model has a dense ferromagnetic ($df$) ground state instead of the ferromagnetic ground state at low temperature region and exhibits the dense ferromagnetic ($df$) - ferromagnetic ($F$) phase transition for $d=D/J=2.9$, $k=K/J=-0.5$, $\ell =L/J=0$ and $h=H/J=0$. The critical behavior of the dense ferromagnetic ($df$) - ferromagnetic ($F$) phase transition has been investigated using the cellular automaton cooling and heating algorithms. The universality class and the type of the dense ferromagnetic ($df$) - ferromagnetic ($F$) phase transition have been researched within the framework of the finite - size scaling, the power law relations and the probability distribution. The results show that the dense ferromagnetic- ferromagnetic phase transition is of the second order and the model shows universal second order Ising critical behavior at $d=2.9$ parameter value through $k=-0.5$ line.

Jonathan V. Selinger