Magnetic ordering in strong anisotropic ferromagnetic bilayers with dipolar and antiferromagnetic interlayer exchange interactions: Monte Carlo approach

J. J. MELO QUINTERO; G. P. SARACCO; M. A. BAB

PHYSICAL REVIEW E - STATISTICAL PHYSICS, PLASMAS, FLUIDS AND RELATED INTERDISCIPLINARY TOPICS

APS

Año: 2024

1063-651X

In this work, multilayer films consisting of two strong-anisotropic ferromagnetic layers antiferromagnetically coupled by a nonmagnetic spacer are studied by Monte Carlo simulations. The system is modeled by an Ising-based Hamiltonian that depends on both the intralayer exchange and dipolar constants, and also on the interlayer exchange constant, IEC. The ground state of the monolayers (null IEC) corresponds to alternate stripe domains with width h defined by the ratio betweenthe exchange and dipolar constants (δ). The results show that IEC alters the energy balance that controls the stripe domain formation, leading to a ground statecharacterized by in-plane stripes out-plane antiferromagnetically coupled. When temperature increases two regimes are identified: an IEC dominated regime where the orientational and positional orders are simultaneously lost in both layers, driving the system to the tetragonal liquid (TL) phase; and a dipolar dominated one where signs of layers decoupling and the onset of positional disorder are observed. The last could be related with an intermediate nematic phase (NM). From the study of the non-equilibrium dynamics, the phase transitions to TL phase are characterized as continuous, while that to NM one as Kosterlitz-Thouless type. Also, for both layers the critical temperatures are the same, and increase with IEC magnitude. Furthermore, the obtained critical exponents depend of the IEC values, which is indicative of a weak universality. For the dipolar dominated regime, the decoupling betweenlayers is also evidenced by the difference between their critical exponents.