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1.
We investigate the electronic transport in a silicene-based ferromagnetic metal/ferromagnetic insulator/ferromagnetic metal tunnel junction. The results show that the valley and spin transports are strongly dependent on local application of a vertical electric field and effective magnetization configurations of the ferromagnetic layers. In particular, it is found that the fully valley and spin polarized currents can be realized by tuning the external electric field. Furthermore, we also demonstrate that the tunneling magnetoresistance ratio in such a full magnetic junction of silicene is very sensitive to the electric field modulation. 相似文献
2.
S.G. Chigarev 《Journal of magnetism and magnetic materials》2009,321(7):891-893
We investigate a perpendicular electric current passing through a “ferromagnetic nanojunction”, that is through some layered nanosized structure of spin-valve type, containing two ferromagnetic metallic layers. Spacer may be used between the metallic layers to prevent the rotation of the moving spin phases. Such an arrangement is typical for spin valves: one of the metallic layers has strongly pinned magnetic lattice and the other one has free magnetic lattice and free mobile spins. Further the conditions are derived to provide a very high nonequilibrium spin injection level. It appears that the so-called spin resistances of the constitutive layers should be in definite relations to each other. These relations lead to the situation where the spin injection becomes dominant and significantly suppresses the “ordinary” spin-transfer torque. As a result, the threshold current becomes lowered down to 2-3 and even more orders of magnitude. 相似文献
3.
A spin valve with two pinned ferromagnetic layers sandwiching a free ferromagnetic layer with a thickness smaller than the
spin diffusion length in the same layer and than the domain wall thickness is considered. The instability conditions are determined
for various mutual orientations of the magnetization of the layers. The possibility of a considerable decrease in the instability
threshold due to joint action of spin-polarized current and an external magnetic field is indicated. It is shown that in addition
to collinear states, a nonequilibrium noncollinear state can exist, into which the system is switched after exceeding the
instability threshold. 相似文献
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5.
A junction between two ferromagnetic metal layers with fixed spins in one of them and free spins in the other (spin valve) is considered. The junction is placed in an external magnetic field that orients the free layer oppositely to the fixed layer. It is shown that the spin-polarized electron flow from the fixed layer to the free layer gives rise to stable motionless magnetic domains in the free layer, provided that the magnetic field and the thickness of the free layer are large enough. 相似文献
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7.
V. L. Mironov A. A. Fraerman B. A. Gribkov O. L. Ermolaeva S. A. Gusev S. N. Vdovichev 《Physics of the Solid State》2010,52(11):2297-2302
The processes of local magnetization reversal of elliptic Co/Si/Co nanodisks under the action of a nonuniform magnetic field
of a magnetic-force microscope (MFM) probe have been investigated. The specific features of the distribution of the phase
MFM contrast from particles with ferromagnetic and antiferromagnetic configurations of the magnetic moments in neighboring
Co layers have been discussed. It has been shown experimentally that, under the action of the probe field, there occur orientational
transitions of two types: transitions from the ferromagnetic configuration to the antiferromagnetic configuration due to the
reorientation of the magnetization of the upper layer and transitions in the antiferromagnetic configuration with a change
in the orientation of the magnetic moment in both ferromagnetic layers. The presented results of micromagnetic simulation
of the processes of transformation of the magnetization in such particles under the action of the MFM probe field explain
the main regularities of the magnetization reversal processes. 相似文献
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9.
Rakesh Kar 《Journal of magnetism and magnetic materials》2010,322(6):671-674
If one applies an rf magnetic field parallel to a strong static field, temperature of a ferromagnetic substance rises due to ferromagnetic resonance. This phenomenon finds immediate application in the field of hyperthermic oncology. In this work, we have found expression for the increase in temperature when a ferromagnetic material is placed under a static and a varying magnetic field of high frequency through spin wave approach. The numerical value of this increment of local temperature has been estimated for yttrium iron garnet (YIG). We also have examined the possibility of enhancing the temperature of a ferromagnetic material only by applying a strong static field. 相似文献
10.
A novel mechanism is proposed for magnetization reversal by the current of magnetic junctions with two metallic ferromagnetic layers and thin separating nonmagnetic layer. The spin-polarized current flows perpendicularly to the interfaces between the ferromagnetic layers, in one of which the spins are pinned and in the other they are free. No domain structure is formed in the ferromagnetic layers. The current breaks spin equilibrium in the free layer, which manifests itself in the injection or extraction of spins. The nonequilibrium spins interact with the magnetization of the lattice due to the effective field of s-d exchange, which is current dependent. At currents exceeding a certain threshold value, this interaction leads to magnetization reversal. Two threshold currents for magnetization reversal have been obtained theoretically, which are reached as the current increases or decreases, respectively. Thus, the phenomenon of current hysteresis is found. The calculated results are in good agreement with experiments on magnetization reversal by current in three-layer junctions of composition Co(I)/Cu/Co(II) prepared in a pillar form. 相似文献
11.
V. Kuncser G. Schinteie P. Palade I. Mustata C. P. Lungu N. Stefan H. Chiriac R. Vladoiu G. Filoti 《Hyperfine Interactions》2009,191(1-3):135-141
Exchange bias and spin valve structures with Fe as ferromagnetic layers selectively enriched in 57Fe and Ir–Mn of different compositions as antiferromagnetic pinning layers have been prepared by r.f. sputtering. Conversion Electron Mössbauer Spectroscopy and Magneto Optic Kerr Effect have shown that the local structure and interactions in the whole ferromagnetic layers, with direct influence on their magnetic reversal processes, depend on growing order of the layers and composition of the AF layer. Interfacial atomic diffusion is the main reason of perturbing the local structure of the ferromagnet. Mössbauer Spectroscopy is a powerfool tool which allows a detailed analysis of local configurations, in order to optimize the magnetic and giant magnetoresistive parameters of such multilayers of important technological applications. 相似文献
12.
S. Gluzman 《Zeitschrift für Physik B Condensed Matter》1993,90(3):313-318
The behaviour of the two-dimensional quantum antiferromagnet of arbitrary spin in a strong transversal magnetic field on a square lattice is studied in terms of the equivalent Bose gas problem. The existence of phase transition from the state characterized by “quasi-long-range” magnetic order to the disordered ferromagnetic state is demonstrated. The expressions for correlation functions, thermodynamical and magnetic characteristics are derived. 相似文献
13.
A finite Heisenberg magnetic ring with an arbitrary single-node spin and two spin deviations from the ferromagnetic saturation
is considered as the system of two Bethe pseudoparticles. The set of all relevant magnetic configurations spans a surface
which can be recognised as a Mőbius strip. The dynamics of the system imposes the double twist of all regular orbits of the
translation symmetry group. 相似文献
14.
The magnetic and resonance properties of cylindrical magnets at first-order phase transition from paramagnetic to ferromagnetic state were theoretically studied. It has been shown that in the external magnetic field directed perpendicularly to the rotation axis, formation of a specific domain structure of paramagnetic and ferromagnetic layers can be energetically favorable. The parameters of cylindrical phase domains as well as their dependences on temperature, magnetic field and material characteristics have been calculated. Peculiarities of the magnetic resonance spectra appearing as a result of the phase domain formation have been considered. Dependence of the resonance field of the system of ferromagnetic domains on magnetization and temperature has been obtained. 相似文献
15.
We study spin dependent transport through a magnetic bilayer graphene nanojunction configured as a two-dimensional normal/ferromagnetic/normal structure where the gate voltage is applied on the layers of ferromagnetic graphene. Based on the four-band Hamiltonian, conductance is calculated by using the Landauer-Buttiker formula at zero temperature. For a parallel configuration of the ferromagnetic layers of bilayer graphene, the energy band structure is metallic and spin polarization reaches its maximum value close to the resonant states, while for an antiparallel configuration the nanojunction behaves as a semiconductor and there is no spin filtering. As a result, a huge magnetoresistance is achievable by altering the configurations of ferromagnetic graphene around the band gap. 相似文献
16.
Stamm C Tudosa I Siegmann HC Stöhr J Dobin AY Woltersdorf G Heinrich B Vaterlaus A 《Physical review letters》2005,94(19):197603
Applying one ultrashort magnetic field pulse, we observe up to 10 precessional switches of the magnetization direction in single crystalline Fe films of 10 and 15 atomic layers. We find that the rate at which angular momentum is dissipated in uniform large angle spin precession increases with time and film thickness, surpassing the intrinsic ferromagnetic resonance spin lattice relaxation of Fe by nearly an order of magnitude. 相似文献
17.
A. D. Talantsev O. V. Koplak G. L. L’vova O. S. Dmitriev S. Petit Watelot Y. Lu S. Mangin R. B. Morgunov 《Physics of the Solid State》2017,59(10):1947-1951
Negative magnetoresistance modifying the quality factor of a microwave cavity under the magnetization switching of ferromagnetic layers has been discovered in a MgO/CoFeB/MgO/Ta film with a single ferromagnetic layer and a MgO/CoFeB/Ta/CoFeB/MgO/Ta spin valve consisting of two ferromagnetic CoFeB layers. The dependence of the first derivative dP/dH of the microwave absorption signal on the dc magnetic field of the spectrometer exactly reproduce the magnetic hysteresis loops of the sample. The slope of these dependences and the amplitude of dP/dH jumps under remagnetization of the layers are determined by the interplay of a negative magnetoresistance of individual layers and a positive giant magnetoresistance of the entire multilayer structure. The discovered phenomenon allows using microwave absorption for making a high-sensitivity contact-free indicator of the basic magnetization states of a spin valve. 相似文献
18.
The influence of an electric field on the ferromagnetic resonance (FMR) in a multilayer magnetic system consisting of two magnetic layers separated by a thin nonmagnetic interlayer has been investigated. It has been shown that, upon the excitation of magnetization oscillations by a microwave magnetic field, the eigenfrequencies of the ferromagnetic resonance depend on the stationary electric field applied in the plane of the layers. It has also been demonstrated that, in this system, high-frequency magnetization oscillations can be excited by an electric microwave field. The results of the investigation of the polarization properties of the excitation mechanism indicate that this effect can be observed experimentally. 相似文献
19.
Yu. V. Gulyaev P. E. Zilberman A. I. Panas E. M. Epshtein 《Journal of Experimental and Theoretical Physics》2008,107(6):1027-1038
We study the passage of transverse current through a ferromagnetic nanojunctions, viz., a layered nanostructure of the spin-valve type containing two ferromagnetic layers separated by a spacer that prevents exchange coupling between the layers in the absence of current, but does not affect spin polarization of the current. The conditions for a high level of injection of spins by current are derived at which the concentration of injected nonequilibrium spins can reach or even exceed their equilibrium concentration. In such conditions, a number of new effects are observed. The threshold of exchange switching by current is lowered by several orders of magnitude due to matching of spin resistances of the layers. The application of an external magnetic field in the vicinity of the orientation phase transition additionally lowers this threshold. This leads to multistability, in which one value of the current corresponds to two (or more) stable noncollinear orientations of magnetization, and switching itself becomes irreversible. A methodical feature of this research is that the calculation is performed in the so-called macrospin approximation, which is in good agreement with most of known experiments. In this approximation, the equations of motion taking into account the torque as well as spin injection are derived for the first time and solved. 相似文献
20.
Yu-Ling Song Yan ZhangJian-Min Zhang Dao-Bang LuKe-Wei Xu 《Physica B: Condensed Matter》2011,406(3):699-704
Combined with three spin configurations, the effects of the dangling bonds on the electronic and magnetic properties of both zigzag edge and armchair edge Si nanoribbions (ZSiNR and ASiNR) have been investigated systematically by the first-principles calculations in the local spin-density function theory. The dangling bonds at one edge or both edges make ZSiNR to transform from ferromagnetic state of the perfect ZSiNR to antiferromagnetic state. However, the dangling bonds at one edge and both edges make ASiNR to transform from nonmagnetic semiconductor of the perfect ASiNR to ferromagnetic and antiferromagnetic metals, respectively. Furthermore, the magnetic moment of the ferromagnetic state increases for the perfect bare one edge and bare both edges successively for either ZSiNR or ASiNR. 相似文献