Two compensation points induced by surface parameters in nanoscaled transverse Ising ferrimagnetic thin films

The phase diagrams and magnetizations of two nanoscaled thin films with a negative interlayer interaction at the surfaces, described by the transverse Ising model, are investigated by the use of the effective field theory with correlations. It is proved that two compensation points induced by the surface parameters (exchange interaction and transverse field at the surfaces) can be found in these nanosystems.     

Compensation point (or points) of nanoscaled transverse Ising thin films: effects of surface dilution

The phase diagram (critical temperature and compensation temperature) and the total magnetizations in a nanoscaled transverse Ising thin film with thickness L and a negative interlayer coupling at the surfaces are investigated by the use of both the effective-field theory with correlations and the mean-field theory. Particular emphasis is given to the effects of the surface and its dilution on them. We have found that, for appropriate values of the system parameters, compensation point (or points) may be obtained in the present system with L?=?5 (or L?=?10).     

Ferrimagnetic magnetizations of transverse Ising thin films with diluted surfaces

The temperature dependences of longitudinal and transverse magnetizations in transverse Ising thin films with diluted surfaces which are coupled antiferromagnetically to the bulk are studied by the use of the effective-field theory (EFT) with correlations. Novel features are obtained for the thermal variations of longitudinal magnetization, being different from those of the bulk ferrimagnetic materials, such as the possibility of two compensation points. They are depending on the thickness of a film and the surface dilution. These characteristic phenomena come from the competition between the surfaces and the bulk when the ratios of the physical parameters (transverse field and exchange interaction) between the surfaces and the bulk are selected as some large values.     

Surface-surface interaction in smectic liquid crystal films

Null transmission ellipsometry was employed to study the field induced transition of the surface arrangements in freestanding films of smectic liquid crystals. The interlayer interaction between the two surfaces obtained from the threshold voltage for the transition is found to be antiferroelectric and is quasilong ranged. The possible microscopic origins of the measured interaction and its relevance to the interlayer interaction in antiferroelectric liquid crystal materials are discussed.     

Frustration in a transverse Ising nanoisland: effects of interlayer coupling

The phase diagram and magnetizations in a transverse Ising nanoisland are examined by using the effective field theory with correlations. The nanoisland is constructed from two layers with nine atoms in each which are coupled by the interlayer coupling. We present some characteristic phenomena in them which come from the frustration induced by an interlayer coupling and two transverse fields.     

Nanoparticle with a ferrimagnetic interlayer coupling in the presence of single-ion anisotropis

The magnetic properties of a nanoparticle described by the transverse Ising model with single-ion anisotropis, which consists of a concentric spin-3/2 core and a hexagonal ring spin-5/2 shell coupled with a ferrimamagnetic interlayer coupling, are studied by the effective-field theory with self-spin correlations. Particular emphasis is given to the effects of the both the transverse field and the single-ion anisotropis on the longitudinal and transverse magnetizations, phase diagrams of the nanoparticle. We have found that, for appropriate values of the system parameters, one or two compensation points may be obtained in the present systems.     

Phase diagrams in an ultra-thin spin-1 transverse Ising film with bond or site dilution at surfaces

The phase diagrams of two nanoscaled thin films with bond and site dilutions at the surfaces, described by the spin-1 transverse Ising model, are investigated by the use of an effective field theory with correlations. A number of characteristic phenomena have been found in them, which are heavily dependent on the ratios (r = J₁/J and p = Ω_S/Ω, where J is the exchange interaction in the inner layer, J₁ is the exchange interaction between the surface and the next inner layer, Ω_S is the transverse field at the surfaces and Ω is the transverse field in the inner layer). Some of them have exhibited very similar behaviors found in the two spin-1/2 nanoscaled thin films with bond and site dilutions at the surfaces.     

Dynamic magnetization reversal and bistable states in antiferromagnetic multilayer structures

The dynamic behavior of the magnetization under a transverse microwave field is investigated in a system of magnetic layers with cubic crystallographic anisotropy coupled through interlayer antiferromagnetic exchange interaction. An orientational phase transition is found to occur as the microwave field frequency and amplitude are varied. It is established that there is a frequency range in which several steady-state regimes of precession of magnetic moments exist. The limits of this range can be efficiently controlled both by varying the strength of the bias magnetic field and the amplitude of the microwave field.     

The possibility of a compensation point induced by a transverse field in transverse Ising nanoparticles with a negative core–shell coupling

The phase diagram and magnetizations of two 2D nanoparticles with a negative core–shell interaction, described by the transverse Ising model, are investigated by the use of the effective field theory with correlations. The behaviors of a compensation point in these nanosystems are examined by changing an applied transverse field. It is proved that a compensation point can be induced in the two nanosystems by applying a transverse field.     

Interlayer interaction mechanism and its regulation on optical properties of bilayer SiCNSs

Silicon carbide nanosheets (SiCNSs) have a very broad application prospect in the field of new two-dimensional (2D) materials. In this paper, the interlayer interaction mechanism of bilayer SiCNSs (BL-SiCNSs) and its effect on optical properties are studied by first principles. Taking the charge and dipole moment of the layers as parameters, an interlayer coupling model is constructed which is more convenient to control the photoelectric properties. The results show that the stronger the interlayer coupling, the smaller the band gap of BL-SiCNSs. The interlayer coupling also changes the number of absorption peaks and causes the red or blue shift of absorption peaks. The strong interlayer coupling can produce obvious dispersion and regulate the optical transmission properties. The larger the interlayer distance, the smaller the permittivity in the vertical direction. However, the permittivity of the parallel direction is negative in the range of 150-300 nm, showing obvious metallicity. It is expected that the results will provide a meaningful theoretical basis for further study of SiCNSs optoelectronic devices.     

Estimation of interlayer interactions in CdI2 by light scattering techniques

The velocity of transverse acoustic wave propagating along the direction perpendicular to the layer and the frequency of the rigid layer mode in CdI₂ have been measured by Brillouin and Raman scattering, respectively, at several temperatures. The interlayer forces have been deduced independently from these two different measurements. A comparison between them has led to the conclusion that the nearest neighbour interlayer interaction dominates the interlayer interaction.     

Magnetic phase transition and the corresponding magnetostriction of intermetallic compounds RMnsGe2（R=Sm,Gd）

The temperature dependence of lattice constants a and c of intermetallic compounds RMn₂Ge₂ (R=Sm, Gd) is measured in the temperature range 10－800K by using the x-ray diffraction method. The magnetoelastic anomalies of lattice constants are found at the different kinds of spontaneous magnetic transitions. The transversal and longitudinal magnetostrictions of polycrystalline samples are measured in the pulse magnetic field up to 25T. In the external magnetic field there occurs a first-order field-induced antiferromagnetism－ferromagnetism transition in the Mn sublattice, which gives rise to a large magnetostriction. The magnitude of magnetostrictions is as large as 10^-3. The transversal and longitudinal magnetostrictions have the same sign and are almost equal. This indicates that the magnetostriction is isotropic and mainly caused by the interlayer Mn－Mn exchange interaction. The experimental results are explained in the framework of a two-sublattice ferrimagnet with the negative exchange interaction in one of the sublattices by taking into account the lattice constant dependence of interlayer Mn－Mn exchange interaction.     

Detection of multi-spin interaction of a quenched XY chain by the average work and the relative entropy

We investigate the nonequilibrium thermodynamics of a quenched XY spin chain with multi-spin interaction in a transverse field. The analytical expressions of both the average work and the relative entropy are obtained under different quenching parameters. The influences of the system parameters on the nonequilibrium thermodynamics are investigated.We find that at finite temperature the critical phenomenon induced by the multi-spin interaction and the external field can be revealed by the properties of the system nonequilibrium thermodynamics. In addition, our results indicate that the average work and the relative entropy can be used to detect both the existence and strength of the multi-spin interaction in the nonequlibrium system.     

Ferroelectric phase transition of a finite alternating superlattice

The phase transition properties of ferroelectric supperlattice with finite alternating layers have been investigated by using the transverse Ising model within the mean field approximation. The effects of surface modification are introduced on the assumption that the exchange interaction and transverse field parameters on the top surface are different from those in other layers of the superlattice. The phase diagrams are described in two different ways. The results indicate that the features of the phase diagrams can be greatly modified by changing the transverse Ising model parameters.     

The oscillatory galvanomagnetic size-effect in multilayered structures

Within the framework of the modified semi-classical Fuchs-Sondheimer model, we investigated theoretically the electrical resistivity of multilayered structures (MLS) consisting of alternating metallic layers (of different purity and different thicknesses) in a transverse magnetic field as functions of the ratio of the adjacent layer thicknesses and the magnetic field value. We have derived both a general formula (valid at arbitrary values of layer thicknesses) and asymptotic expressions that are valid when metallic layers are thick or thin compared with the electron mean free path. We found a non-monotonic behavior in the resistivity vs. the value of an applied magnetic field. As we demonstrated, this behavior is sensitive to the characteristics of the electron scattering in the interlayer interfaces in low magnetic fields. Moreover, the MLS resistivity oscillates in high magnetic fields with the field value (or with the layer thicknesses). The oscillation includes the harmonics that correspond both to the each layer thicknesses and the total thickness. The intensity of the oscillation is determined by the diffusive electron scattering in the interfaces, and the oscillation amplitude is proportional to the coefficient of the electron transmission through the interlayer interfaces. We have calculated numerically the resistivity in a wide range of fields and layer thicknesses at various values of the parameters of the interface and bulk electron scattering.      

Angular dependent negative magnetoresistance in Si-MOS (111) inversion layers

The negative transverse magnetoresistance effect was observed in n-inversion layers in Si-MOS (111) surfaces at temperatures between 1.5 and 8.3 K. The negative magnetoresistance depends only on the normal component of the magnetic field to the surface and has a saturation value at high fields. The difference between the resistivity at zero field and that at saturation field increases logarithmically with decreasing temperature such as the effect due to the s-d scattering (Kondo effect).     

Transport properties of AB-stacked bilayer graphene nanoribbons in an electric field

The electronic and thermal properties of AB-stacked bilayer graphene nanoribbons subject to the influences of a transverse electric field are investigated theoretically, including their transport properties. The dispersion relations are found to exhibit a rich dependence on the interlayer interactions, the field strength, and the geometry of the layers. The interlayer coupling will modify the subband curvature, create additional band-edge states, change the subband spacing or energy gap, and separate the partial flat bands. The bandstructures will be symmetric or asymmetric about the Fermi energy for monolayer or bilayer nanoribbons, respectively. The inclusion of a transverse electric field will further alter the bandstructures and lift the degeneracy of the partial flat bands. The chemical-potential-dependent electrical and thermal conductance exhibit a stepwise increase behavior. Variations in the electronic structures with field strength will be reflected in the electrical and thermal conductance. Prominent peaks, as well as single-shoulder and multi-shoulder structures in the electrical and thermal conductance are predicted when varying the electric field strength. The features of the conductance are found to be strongly dependent on the field strength, the geometry, interlayer interactions and temperature.     

Some characteristic phenomena in a transverse Ising nanotube

The phase diagram and magnetizations of a cylindrical nanotube described by the transverse Ising model are investigated by the use of the effective field theory with correlations. Some comparisons between the nanotube and the nanowire have been given for the phase diagrams. In particular, the temperature dependences of longitudinal magnetization in the system with a negative shell–core interaction are investigated. Some characteristic phenomena (new types in ferrimagnetism) which have not been observed in the nanowire as well as similar phenomena are found in the thermal variations, depending on the ratio of the physical parameters in the surface shell and the core. The possibilities of two compensation points and a field induced compensation point in the nanotube are also discussed.     

Effect of optical radiation on magnetic resonance in Fe/Si/Fe trilayer films

A photoinduced change in the magnetic resonance parameters is observed in trilayer films of the system Fe/Si/Fe. The shifts of the resonance field and the character of the interlayer interaction are investigated as functions of the temperature, illumination of the films, and thickness of the silicon interlayer. It is found that at low temperatures the photoinduced contribution to the exchange interaction constant between the iron layers is antiferromagnetic. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 4, 287–290 (25 August 1998)     

The random transverse Ising thin film with decorated ferrimagnetic surfaces

The phase diagrams and magnetization curves of the random transverse Ising film with decorated spin-1 atoms on the surface are investigated by the use of an effective field method within the framework of a single cluster theory. In particular, the case in which decorated atoms at the surfaces are ordered ferrimagnetically is examined. The effects of the interactions, random transverse field at the surface and in the bulk, and film thickness are studied. A number of characteristic phenomena, such as the possibility of compensation points on the surfaces and in the film are found.