Perturbation Expansions of the Ground State Energy of the Antiferromagnetic ANNNI Model in Two Perpendicular External Magnetic Fields


By Kunle Adegoke

ABSTRACT

Using Rayleigh-Schrödinger perturbation theory, we derive analytic expressions for the ground state energy of the antiferromagnetic Axial Next Nearest Neighbour Ising (ANNNI) model in two mutually orthogonal external magnetic fields. Expressions for various physical quantities are also derived. The calculations are carried out to the fourth order in the transverse field.  

Keywords: Perturbation expansions, ANNNI model,  magnetic fields, order parameters 

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