共查询到20条相似文献,搜索用时 0 毫秒
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C. Rau 《Applied Physics A: Materials Science & Processing》1989,49(6):579-587
The critical behavior, ferromagnetic order and magnetic anisotropies of ultrathin, epitaxial, magnetic films is studied using electron capture spectroscopy (ECS), which is capable of probing the long-ranged and short-ranged electron spin polarization (ESP) at the topmost surface layer of uncoated and coated magnetic structures. For all systems [Ni(100)/Cu(100), Ni(100)/NaCl(100), fcc Fe(111)/Cu(111), Fe(100)/Ag(100), Tb/Fe(100)/Ag(100), Fe(100)/Au(100), hcp Tb(0001)/W(110), Fe(110)/W(110), V(100)/Ag(100), Pd(100)/Ag(100), Pd/W(110)] investigated so far, ferromagnetic order is detected. It is found that the surface Curie temperatureT
Cs depends on film thicknessd. ECS data obtained at the surface of various systems reveal the existence ofT- andd-dependent magnetic anisotropies. Although for V(100)/Ag(100) the measured critical exponent=0.128 agrees very well with=1/8 predicted for the two-dimensional Ising model, for other systems, such as Fe(100)/Au(100), the measured value (0.25) is in disagreement with theoretical predictions. The experimental results are discussed within the framework of presently available experimental and theoretical data. 相似文献
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It is shown that the pair breaking parameter of the Maki-Thompson contributions to the fluctuation conductivity above the superconducting transition temperature has the same thickness dependence as the transition temperature depression in very thin amorphous Be-Al films. Both can be ascribed to an extremely thin surface sheath with suppressed superconductivity.Supported by the Swedish Natural Science Research Board. 相似文献
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A. V. Vashkovskii E. G. Lokk 《Bulletin of the Russian Academy of Sciences: Physics》2007,71(11):1604-1606
Some effects and phenomena that can be implemented in ferrite films using dipole spin or magnetostatic waves are described. 相似文献
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We derive the extended string order parameter O(S) for antiferromagnetic Heisenberg chains with half-integer spin S in the valence-bond-solid picture. We obtain the analytic power-law scaling of O(S) versus the chain length L and show that O(S) scales at an extremely slow pace that decreases rapidly with growing spin magnitude. Furthermore, accurate numerical calculations show that the power-law scaling sets in only when L exceeds a characteristic length scale l(S) which increases very fast with growing S. Consequently, a pseudo-long-range string order exists in half-integer-spin Heisenberg chains. The implications of this result and its relationship to other topological features such as the end-chain states are discussed. 相似文献
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We demonstrate the existence of nonlocal topological (string) order in half-integer-spin antiferromagnetic Heisenberg chains on macroscopic scale on the basis of analytical scaling analysis and density matrix renormalization group calculations. Strong numerical evidence leads to a conjecture that chains with S = (2m-1)/2 and m (m = integers) belong to the same topological class defined by the topological angle theta/pi = 1/m that plays a role similar to the fictitious gauge field in the fractional quantum Hall effect. 相似文献
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Moreo A 《Physical review. B, Condensed matter》1994,49(18):13172-13174
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It is well known that there are two possible switching mechanisms in ferroelectric crystals and films (see, e.g., Tagantsev et al 2010 Domains in Ferroic Crystals and Thin Films (Berlin: Springer)). The first mechanism, which follows from the mean-field theory of Landau-Ginzburg, is a homogeneous one and does not connect domains. This mechanism was never observed before 1998. The second mechanism, connected with nucleation and domain movement, is common for the ferroelectrics and is well known from the time of domain discovery (1956). In the present paper the existence of a homogeneous mechanism of switching in ultrathin copolymer films is confirmed by piezoresponse force microscopy. The results of the present paper permit us to suppose that homogeneous switching exists in other ultrathin ferroelectric films. 相似文献
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T. Chattopadhyay H. v. Löhneysen T. Trappmann M. Loewenhaupt 《Zeitschrift für Physik B Condensed Matter》1990,80(2):159-160
The magnetic ordering previously discovered in CeCu6–xAux heavy-fermion alloys is shown to be of long-range antiferromagnetic type by elastic neutron scattering performed on a polycrystalline sample. The data are compatible with an incommensurate wave vector (0.17, 0, 0.514). Although a definite assignment needs a single-crystal study, the magnetic structure is clearly different from the type of magnetic correlations in pure CeCu6 found in inelastic scattering. 相似文献
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The resonance mode spectrum in films on antiferromagnetic substrates with rigid pinning of the magnetic moment at film-substrate boundary was investigated. Two cases are considered: an external field is antiparallel or perpendicular to the pinning direction. 相似文献
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Martin Schreiber Gareth P. Keeley Markus Boese Georg S. Duesberg 《Applied Surface Science》2010,256(21):6186-17
Ultrathin conductive carbon layers (UCCLs) were created by spin coating resists and subsequently converting them to conductive films by pyrolysis. Homogeneous layers as thin as 3 nm with nearly atomically smooth surfaces could be obtained. Layer characterization was carried out with the help of atomic force microscopy, profilometry, four-point probe measurements, Raman spectroscopy and ultraviolet-visible spectroscopy. The Raman spectra and high-resolution transmission electron microscopy image indicated that a glassy carbon like material was obtained after pyrolysis. The electrical properties of the UCCL could be controlled over a wide range by varying the pyrolysis temperature. Variation in transmittance with conductivity was investigated for applications as transparent conducting films. It was observed that the layers are continuous down to a thickness below 10 nm, with conductivities of 1.6 × 104 S/m, matching the best values observed for pyrolyzed carbon films. Further, the chemical stability of the films and their utilization as transparent electrochemical electrodes has been investigated using cyclic voltammetry and electrochemical impedance spectroscopy. 相似文献
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The nanodynamics of ferroelectric ultrathin films made of PbTi(0.6)Zr(0.4)TiO(3) alloy is explored via the use of a first-principles-based technique. Our atomistic simulations predict that the nanostripe domains which constitute the ground state of ferroelectric ultrathin films under most electric boundary conditions oscillate under a driving ac field. Furthermore, we find that the atomically thin wall, or nanowall, that separates the nanodomains with different polarization directions behaves as an elastic object and has a mass associated with it. The nanowall mass is size-dependent and gives rise to a unique size-driven transition from resonance to relaxational dynamics in ultrathin films. A general theory of nanodynamics in such films is developed and used to explain all computational findings. In addition, we find an unusual dynamical coupling between nanodomains and mechanical deformations that could potentially be used in ultrasensitive electromechanical nanosensors. 相似文献
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J. Bai S. F. Fu S. Zhou X. Z. Wang 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):343-348
We investigate one magnetically nonlinear response of antiferromagnetic (AF) films to
incident electromagnetic waves, or the reflective optical bi-stability (ROB). Such
geometry is used, where the AF anisotropy axis and external static magnetic field both are
parallel to the film surfaces and normal to the incident plane. For TE incident waves with
the electric component transverse to the incident plane, the ROB of the AF film with the
absorption is calculated, but the case of TM incident waves is neglected since no magnetic
nonlinearity is induced in this geometry. The bi-stability is completely different in the
two resonant-frequency vicinities. Two kinds of bi-stability are found in the higher
vicinity, and their features versus incident power are opposite. We also find that there
are critical incident angle and critical film thickness for the existence of bi-stability.
The bi-stability disappears when the film thickness or incident angle exceeds its critical
value. Because the properties of bi-stable reflection sensitively depend on the external
field and the incident angle, this bi-stability can be easily modulated by means of
changing these quantities. 相似文献