共查询到20条相似文献,搜索用时 46 毫秒
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We have investigated the spin and orbital moments of Ir-based double perovskites with (n = 3, 4, 5) states by local spin-density approximation with spin-orbital coupling and Hubbard correlation (LSDA+SOC+U). Our calculations reveal that the ratio of orbital to spin momentum approaches to certain values for the double perovskites with different 5dn (n = 3, 4, 5) shell fillings. Based on d orbits, a spin-orbital coupling model with exchange splitting is proposed and it can well describe the ratio of angular momentums for the compounds. Our model calculations reveal that is determined by the exchange splitting, spin-orbital coupling as well as the state of shell filling. Our model is well corroborated by the experiments and density-functional calculations. 相似文献
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In the present work are reported the stress annealing (SA) effect on magnetic properties of Fe–Al–B alloys and the result on the piezomagnetic coefficient , where σ is the applied stress, B is the magnetic induction and H is the applied magnetic field. The objective is to evaluate the potential use of these alloys as smart materials of force sensors. The study comprises two alloys with compositions (Fe0.87Al0.13)98.4B1.6 (Al13) and (Fe0.82Al0.18)98.4B1.6 (Al18). The microstructure, hysteresis loops and B vs. were analyzed before and after the SA. Regarding the force sensitivity, the SA increased the piezomagnetic coefficient due the introduction of an extrinsic anisotropy in both Fe–Al–B alloys. Moreover, the stress range, in which the piezomagnetic coefficient is linear, is higher after the SA. Concerning the single phase (Fe0.87Al0.13)98.4B1.6 alloy, the force/pressure sensitivity and the linear stress range increase up to 16.8% and 47.1%, respectively. For the two phase (Fe0.82Al0.18)98.4B1.6 alloy, the increase was a bit higher, but the curves B vs. σ are hysteretic, spoiling the use of this material as a force sensor component. 相似文献
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《Physics letters. A》2020,384(27):126687
We investigate the phase transitions in the Ising model on a layered square lattice with first-() and second-() neighbor intralayer interactions and interlayer couplings (J). The thermodynamics of the system is evaluated within a cluster mean-field approximation, which allows us to identify the nature of the thermally driven phase transitions hosted by the model. As a result, we find that interlayer couplings reduce the region of first-order phase transitions between paramagnetic and superantiferromagnetic states. We also find that the interlayer couplings reduce the frustration effects by reducing the entropy content of the low-temperature phases. Our results suggest that tricriticality is present in the special case , which is in qualitative agreement with recent Monte Carlo simulations for the model. 相似文献
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S. Nazir 《Physics letters. A》2019,383(16):1977-1982
Interfacial magnetism and magnetic anisotropy constant () in Co/MgO heterostructure have been studied using ab-initio density functional calculations. It is found that interfacial Co spin magnetic moment shows a strong interdependence on Co-O bond lengths and a reasonable spin-polarization of ~80% is established as a function of Co layers. Our results revealed a saturated positive (out-of-plane) of +2.80 mJ/m2 at ≥12 Co layers (~1.6 nm Co thickness), which is associated with orbital magnetic moment difference in [100] and [001] direction along with a strong hybridization between and orbitals through orbital angular momentum operator . Furthermore, it is shown that the magnitude almost remains constant and weakens in the case of under- and over-oxidations in the interfacial MgO and Co layers, respectively. Interestingly, improved for oxygen migrated interface due to enhanced and orbitals coupling. The disordered interfaces stability is checked by analyzing the formation energy. Hence, the present findings disclose that the higher Co thickness in ordered Co/MgO structure supports to out-of-plane [001] (positive) , which could be useful for its technological implementation in high-density magnetic data storage devices with high thermal stability. 相似文献
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《Physics letters. A》2020,384(19):126399
In this work we investigate a generalized tunneling barrier for planar emitters at zero-temperature. We present the evidence of the emergence of a non-Fowler-Nordheim-type general behavior for the field emission current density in the case that the Fermi energy (μ) is comparable with or smaller that the decay width (). Therefore, for some non-metals or materials that have very small Fermi energy the standard Fowler-Nordheim-type theory may require a correction. In the opposite regime, i.e., for μ much larger that , we confirm that the conventional theory is suitable for metals. 相似文献
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B. Krunavakarn 《Physics letters. A》2019,383(12):1341-1344
We consider a superconducting spin valve in multiply connected superconductor-ferromagnet hybrid geometry such as a superconducting ring enclosed a ferromagnetic metal, in the framework of linearized Usadel equations. We simplify our model by considering the presence of the exchange field in the superconducting ring which allows us to manipulate magnetization orientations in parallel or antiparallel configurations by switching the weaker exchange field. In such geometry the superconducting ground state is activated to higher orbital states characterized by the nonvanishing vorticity parameters L which will be the energetically favorable superconducting state in some ranges of the proximity superconductor-ferromagnet region. The competing effects caused by the exchange interactions and the orbital effect, are analyzed through the nonmonotonic dependence of the superconducting critical temperature on the radius of the ferromagnetic core. The analytic formula is obtained within the single mode approach and the analysis of the spin switch effect is given. 相似文献
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Chao Liu Liying Wang Lin Yang Famei Wang Chunhong Xu Jingwei Lv Guanglai Fu Xianli Li Qiang Liu Haiwei Mu Tao Sun Paul K. Chu 《Physics letters. A》2019,383(25):3200-3206
A single-polarization filter comprising a gold-coated photonic crystal fiber based on surface plasmon resonance is designed and investigated. The pattern matching and coupled polarization characteristics analyzed by the full-vector finite element method (FEM) and losses at 1,540 nm are achieved to 1,016.01739 dB/cm (x-pol core mode) and 33.81917 dB/cm (y-pol core mode). The crosstalk (CT) value of the 1,540 nm band is ?853.12653 dB for fiber length and the bandwidth is 850 nm. The working wavelength of the filter ranges from 1,280 nm to 1,540 nm by varying the diameter of outer air holes (), the diameter of inner air holes (), the metal film thickness (t), as well as the liquid refractive index (n). 相似文献
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《Physics letters. A》2020,384(31):126815
(Ga, Mn)As dilute magnetic semiconductor (DMS) is very promising for future spintronic devices, however, the lower Curie temperature () limits the applications. Here, using first-principles calculation based on density functional theory, we investigate the effect of the surface dangling bonds (SDBs) on the magnetic properties of Mn-doped GaAs nanowires (NWs). The results show that As (Ga)-SDBs are equivalent to holes (electrons) doping, giving rise to the magnetic moments on the surfaces of GaAs NWs. Further in the Mn-doped GaAs NWs, the SDBs can effectively regulate the total magnetic moments, due to charge transfers between the Mn-3d orbitals and the residual SDBs, which is analyzed by a carrier modulation model. Most importantly, the As-SDBs can stabilize the ferromagnetic (FM) states and enhance the in Mn-doped GaAs NWs because of their shallow acceptor level with lower energy compared with Mn-3d level. 相似文献
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Alexander S. Balankin M.A. Martínez-Cruz O. Susarrey-Huerta L. Damian Adame 《Physics letters. A》2018,382(1):12-19
We study how fractal features of an infinitely ramified network affect its percolation properties. The fractal attributes are characterized by the Hausdorff (), topological Hausdorff (), and spectral () dimensions. Monte Carlo simulations of site percolation were performed on pre-fractal standard Sierpiński carpets with different fractal attributes. Our findings suggest that within the universality class of random percolation the values of critical percolation exponents are determined by the set of dimension numbers (, , ), rather than solely by the spatial dimension (d). We also argue that the relevant dimension number for the percolation threshold is the topological Hausdorff dimension , whereas the hyperscaling relations between critical exponents are governed by the Hausdorff dimension . The effect of the network connectivity on the site percolation threshold is revealed. 相似文献
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First principle calculations have been employed to investigate the effects of Y concentration, pressure and temperature on various properties of () alloys using density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) is used to perform the calculated results of this paper. Phase stability of alloys is studied using the total energy versus unit cell volume calculations. The equilibrium lattice parameters of these alloys are in good agreement with the available experimental results. The mechanical stability of alloys is proved using elastic constants calculations. Also, the influence of Y concentration on elastic properties of alloys such as Young's modulus, shear modulus, Poisson's ratio and anisotropy factor are investigated and analyzed. By considering both Pugh's ratio and Poisson's ratio, the ductility and brittleness of these alloys are studied. In addition, the total density of states and orbital's hybridizations of different atoms are investigated and discussed. Moreover, the effect of pressure and temperature on some important thermodynamic properties is investigated. 相似文献