14 research outputs found
Hysteresis and the dynamic phase transition in thin ferromagnetic films
Hysteresis and the non-equilibrium dynamic phase transition in thin magnetic
films subject to an oscillatory external field have been studied by Monte Carlo
simulation. The model under investigation is a classical Heisenberg spin system
with a bilinear exchange anisotropy in a planar thin film geometry with
competing surface fields. The film exhibits a non-equilibrium phase transition
between dynamically ordered and dynamically disordered phases characterized by
a critical temperature Tcd, whose location of is determined by the amplitude H0
and frequency w of the applied oscillatory field. In the presence of competing
surface fields the critical temperature of the ferromagnetic-paramagnetic
transition for the film is suppressed from the bulk system value, Tc, to the
interface localization-delocalization temperature Tci. The simulations show
that in general Tcd < Tci for the model film. The profile of the time-dependent
layer magnetization across the film shows that the dynamically ordered and
dynamically disordered phases coexist within the film for T < Tcd. In the
presence of competing surface fields, the dynamically ordered phase is
localized at one surface of the film.Comment: PDF file, 21 pages including 8 figure pages; added references,typos
added; to be published in PR
Exchange anisotropy and the dynamic phase transition in thin ferromagnetic Heisenberg films
Monte Carlo simulations have been performed to investigate the dependence of
the dynamic phase behavior on the bilinear exchange anisotropy of a classical
Heisenberg spin system. The system under consideration is a planar thin
ferromagnetic film with competing surface fields subject to a pulsed
oscillatory external field. The results show that the films exhibit a single
discontinuous dynamic phase transition (DPT) as a function of the anisotropy of
the bilinear exchange interaction in the Hamiltonian. Furthermore there is no
evidence of stochastic resonance (SR) associated with the DPT. These results
are in marked contrast to the continuous DPT observed in the same system as a
function of temperature and applied field strength for a fixed bilinear
exchange anisotropy.Comment: 11 pages including 3 figure pages; submitted to PR
Dynamic phase transitions in thin ferromagnetic films
Monte Carlo simulations have been used to investigate the dynamic phase
behavior of a classical Heisenberg spin system with a bilinear exchange
anisotropy in a planar thin film geometry. Studies of the field amplitude,
frequency and temperature dependence show dynamic phase transitions in films
subject to a pulsed oscillatory external field. Thin films with competing
surface fields show separate and distinct dynamic phase transitions for the
bulk and surface layers of the film. Between the two transitions, a mixed state
with coexisting dynamically ordered and dynamically disordered phases is
observed in the film. In contrast, the free film with no surface fields shows a
single dynamic phase transition as in a bulk system.Comment: 25 pages including figures in pdf format, to be published in PR
Magneto-Electric Effect for Multiferroic Heterostructures by Monte Carlo Simulation
Magneto-electric effect in a multiferroic heterostructure thin film has been investigated through the use of Monte Carlo simulations. The classical anisotropic Heisenberg model used consists of the interaction energy, the uniaxial anisotropic energy, and the Zeeman energy. The purpose of this article is to demonstrate the dynamic response of polarization is driven by an external magnetic field, when there is a linear magneto-electric coupling between the ferromagnetic and ferroelectric components