Showing papers by "Kostya S. Novoselov published in 2002"
TL;DR: In this article, the authors report quenching of the Hall effect with increasing magnetic field confined in a micron-sized spot, which is explained by a rapid increase in the number of electrons that are scattered or quasilocalized by the magnetic region.
Abstract: We report quenching of the Hall effect with increasing magnetic field confined in a micron-sized spot. Such fields were created by placing tall ferromagnetic pillars on top of a two-dimensional electron gas, which allowed us to achieve the field strength up to 0.4 T under the pillars in the absence of external field. The quenching is accompanied by an anomalous increase in resistance and occurs when the cyclotron diameter matches the size of the magnetic spot. The results are explained by a rapid increase in the number of electrons that are scattered or quasilocalized by the magnetic region.
41 citations
TL;DR: In this article, magnetization studies of individual ferromagnet-superconductor (FS) structures of submicron size were conducted and it was found that FS structures change their magnetization spontaneously.
Abstract: We report magnetization studies of individual ferromagnet-superconductor (FS) structures of submicron size. Upon cooling through the superconducting transition in zero field, such structures are found to change their magnetization spontaneously. We attribute this effect to reshuffling of domains in the ferromagnet, which is caused by temperature-dependent screening of domain's stray fields by the superconductor. The spontaneous magnetization is not localized to the actual contact area between the two materials but can propagate along the ferromagnet as far as several microns from the FS interface.
29 citations
TL;DR: In this paper, the authors studied the movement of domain walls in uniaxial garnet films by means of micromagnetization measurements using miniature gold and semiconductor Hall probes and found that at low (helium) temperatures, the domain walls are found to move by discrete jumps.
Abstract: Nanometer-scale movements of domain walls in uniaxial garnet films have been studied by means of micromagnetization measurements using miniature gold and semiconductor Hall probes. The high spatial resolution is achieved due to low intrinsic noise of semiconductor ballistic Hall microprobes. At low (helium) temperatures, the domain walls are found to move by discrete jumps, which we attribute to pinning on isolated defects, and we were able to measure local hysteresis loops associated with pinning on individual pinning centers. The temperature dependence of the coercive field of a single pinning center allowed us to evaluate the characteristic energy and characteristic volume of the pinning center. At higher temperatures, the character of domain wall propagation changed, and walls were found to move not only by jumps between pinning centers but also via elastic bending.
9 citations
TL;DR: In this paper, the suppression of the Hall effect in a mesoscopic Hall cross with a strong magnetic field only in the center and vanishingly small outside is reported, due to a sharp increase of the number of backscattered and quasi-localised electron orbits.
Abstract: We report the suppression of the Hall effect in a mesoscopic Hall cross with a strong magnetic field only in the centre and vanishingly small outside. The local magnetic field is produced by placing Dy pillar on top of a structure with a high-mobility two-dimensional electron gas. The effect is found to be due to a sharp increase of the number of back-scattered and quasi-localised electron orbits. The possibility of localising electrons inside the magnetic inhomogeneity region is discussed.
4 citations
TL;DR: In this paper, the binding energies of X-XY and X-Z-related donors at the center of a 5-nm AlAs barrier were determined for a GaAs/AlAs/GaAs single-barrier heterostructures.
Abstract: Magnetotransport in GaAs/AlAs/GaAs single-barrier heterostructures, incorporating unintentional donors in the barrier, is studied. Resonant tunneling is observed through the quasiconfined states in the AlAs layer which originate from the X-XY and X-Z conduction-band minima and through two distinct states of the donors bound to the X-XY and X-Z valleys. This allowes us to determine directly the binding energies of X-XY- and X-Z-related donors at the center of a 5-nm AlAs barrier as E-B(X-XY)approximate to70 meV and E-B(X-Z)approximate to50 meV, respectively. Furthermore, we observe an additional oscillatory fine structure of the donor resonances which we attribute to a difference in the binding energies of donors located at different position in the AlAs layer. (Less)
4 citations
TL;DR: Magnetotransport in GaAs/AlAs/GaAs single-barrier heterostructures incorporating unintentional donors in the barrier is studied in this paper, where Resonant tunnelling was observed both through the quasiconfined states in the AlAs layer which originated from the XXY and XZ conduction band minima and through two distinct states of the donors bound to the XZ valleys.
Abstract: Magnetotransport in GaAs/AlAs/GaAs single-barrier heterostructures incorporating unintentional donors in the barrier is studied. Resonant tunnelling was observed both through the quasiconfined states in the AlAs layer which originated from the XXY and XZ conduction band minima and through two distinct states of the donors bound to the XXY and XZ valleys. Furthermore, we observed an additional oscillatory fine structure of the donor resonances which we attribute to the difference in binding energies of donors located at different position of the AlAs layer. Magnetic field behaviour of the fine structure shows that the binding energy of X-related donors depends on both magnetic field and donor position in the barrier.
2 citations