Thickness dependent Curie temperature and power-law behavior of layering transitions in ferromagnetic classical and quantum thin films described by Ising, XY and Heisenberg models

Abstract

Ferromagnetic-paramagnetic phase transitions in classical and quantum thin films have been studied up to 50 monolayers using effective field theory with two-site cluster approximation. Variation of the Curie temperature as a function of film thickness has been examined. The relative shift of the Curie temperature from the corresponding bulk value has been investigated in terms of the shift exponent λ. We have found that shift exponent λ clearly depends on the strength of the ferromagnetic exchange coupling of the surface. Moreover, we have not observed any significant difference between classical and quantum exponents for a particular model.

The Influence of Thickness on the Magnetic Properties of Nanocrystalline Thin Films: A Computational Approach

“…For a monocrystalline film, the critical exponent obtained was ν = 0.66 ± 0.04. This value is between 0.71 and 0.5238, as reported for thin films under a classical Heisenberg model in [38] and [39], respectively. Due to the instability observed in polycrystalline samples, fitting above 16 muc is very complicated to obtain, as it presents high deviation.…”

Effect of exchange interaction in ferromagnetic superlattices: A Monte Carlo study

“…This value is superior to those obtained by high temperature series expansions [22] and those obtained by effective field theory. [23,24] Figure 3 shows the variations of magnetization and magnetic susceptibilities with reduced temperature T /J aa for R 2 = J ab /J aa = 0.2, 1.5, 3, 5 with ∆ /J aa = 0.0, h/J aa = 0.4, and R 1 = R 3 = R 4 = 1.0. The critical temperature is not very sensible with exchange interaction increasing.…”