1,182 research outputs found
Interfacial effects on the polarization of films
By considering an interfacial layer between the electrode and the
() layer, the polarization and the hysteresis behavior of
film are simulated. It is found that the non-ferroelectric interface will
increase the coercive field, and remarkably suppress the polarization of the
ultrathin film under low applied fields. Due to the competition between the
interfacial effect and the internal compressive stress, the maximum
polarization on the P-E loop of a film can be independent on the film
thickness under an adequate applied field.Comment: 3 pages, 2 figure
Ground state and constrained domain walls in Gd/Fe multilayers
The magnetic ground state of antiferromagnetically coupled Gd/Fe multilayers
and the evolution of in-plane domain walls is modelled with micromagnetics. The
twisted state is characterised by a rapid decrease of the interface angle with
increasing magnetic field. We found that for certain ratios M(Fe):M(Gd), the
twisted state is already present at low fields. However, the magnetic ground
state is not only determined by the ratio M(Fe):M(Gd) but also by the
thicknesses of the layers, that is the total moments of the layer. The
dependence of the magnetic ground state is explained by the amount of overlap
of the domain walls at the interface. Thicker layers suppress the Fe aligned
and the Gd aligned state in favour of the twisted state. Whereas ultrathin
layers exclude the twisted state, since wider domain walls can not form in
these ultrathin layers
Magnetodielectric coupling in a triangular Ising lattice
Dielectric constant measurement under magnetic field is an efficient
technique to study the coupling between charges and spins in insulating
materials. For magnetic oxides, the geometric frustration is known to be a key
ingredient to observe such a coupling. Measurements for the triangular
Ising-like cobaltite Ca3Co2O6 have been made. Single crystals of Ca3Co2O6 are
found to exhibit a magnetodielectric effect below TN=25K with a peak in the
e(H) curve at the ferri to ferromagnetic transition. This relation between e
and magnetization has been modelized by using two order parameters in an energy
expansion derived from the Landau formalism and the fluctuation-dissipation
theorem. This result emphasizes the great potential of insulating transition
metal oxides for the search of magnetodielectric effect
Flexomagnetoelectric effect in bismuth ferrite
There is a profound analogy between inhomogeneous magnetoelectric effect in
multiferroics and flexoelectric effect in liquid crystals. This similarity
gives rise to the flexomagnetoelectric polarization induced by spin modulation.
The theoretical estimations of flexomagnetoelectric polarization agree with the
value of jumps of polarization in magnetoelectric dependences (~20muC/m^2)
observed at spin cycloid suppression at critical magnetic field 200kOe.Comment: 6 pages,2 figure
Microvasculaire vrije lap-reconstructies in de mondholte en orofarynx: Naar een betere kwaliteit van leven
Reconstructive objectives after major head and neck surgery include adequate wound healing and optimal residual function. The most appropriate means to achieve this is through the applications of microvascular free flaps. Mainly defects in the oral cavity and oropharynx are reconstructed in this way. The most often used flap is the free radial forearm flap. When bulk or bone is needed other free flaps such as the rectus abdominis flap, the lattisimus dorsi flap, fibula flap or iliac crest flap can be used. The overall success rate is more than 90% and is mainly determined by the patency of the vessels. Comorbidity is an important prognostic factor. Using free flap reconstructions a good quality of life can be achieved. The costs of free flap reconstructions are not higher than reconstructions using pedicled flaps
Atomic and electronic structure of twin growth defects in magnetite
We report the existence of a stable twin defect in Fe3O4 thin films. By using aberration corrected scanning transmission electron microscopy and spectroscopy the atomic structure of the twin boundary has been determined. The boundary is confined to the (111) growth plane and it is non-stoichiometric due to a missing Fe octahedral plane. By first principles calculations we show that the local atomic structural configuration of the twin boundary does not change the nature of the superexchange interactions between the two Fe sublattices across the twin grain boundary. Besides decreasing the half-metallic band gap at the boundary the altered atomic stacking at the boundary does not change the overall ferromagnetic (FM) coupling between the grains
Atomic and electronic structure of twin growth defects in magnetite
We report the existence of a stable twin defect in Fe3O4 thin films. By using aberration corrected scanning transmission electron microscopy and spectroscopy the atomic structure of the twin boundary has been determined. The boundary is confined to the (111) growth plane and it is non-stoichiometric due to a missing Fe octahedral plane. By first principles calculations we show that the local atomic structural configuration of the twin boundary does not change the nature of the superexchange interactions between the two Fe sublattices across the twin grain boundary. Besides decreasing the half-metallic band gap at the boundary the altered atomic stacking at the boundary does not change the overall ferromagnetic (FM) coupling between the grains
Enhanced magnetic moment and conductive behavior in NiFe2O4 spinel ultrathin films
Bulk NiFe2O4 is an insulating ferrimagnet. Here, we report on the epitaxial
growth of spinel NiFe2O4 ultrathin films onto SrTiO3 single-crystals. We will
show that - under appropriate growth conditions - epitaxial stabilization leads
to the formation of a spinel phase with magnetic and electrical properties that
radically differ from those of the bulk material : an enhanced magnetic moment
(Ms) - about 250% larger - and a metallic character. A systematic study of the
thickness dependence of Ms allows to conclude that its enhanced value is due to
an anomalous distribution of the Fe and Ni cations among the A and B sites of
the spinel structure resulting from the off-equilibrium growth conditions and
to interface effects. The relevance of these findings for spinel- and, more
generally, oxide-based heterostructures is discussed. We will argue that this
novel material could be an alternative ferromagetic-metallic electrode in
magnetic tunnel junctions.Comment: accepted for publication in Phys. Rev.
- …