Resistance spikes and domain wall loops in Ising quantum Hall ferromagnets

We explain the recent observation of resistance spikes and hysteretic transport properties in Ising quantum Hall ferromagnets in terms of the unique physics of their domain walls. Self-consistent RPA/Hartree-Fock theory is applied to microscopically determine properties of the ground state and domain-wall excitations. In these systems domain wall loops support one-dimensional electron systems with an effective mass comparable to the bare electron mass and may carry charge. Our theory is able to account quantitatively for the experimental Ising critical temperature and to explain characteristics of the resistive hysteresis loops.Comment: 4 pages, 3 figure

Determinacijska i taksonomska problematika fosilne paleogenske makroflore iz Slovenije i Hrvatske

This paper discusses the complexity of the determination and taxonomy of Palaeogene fossil floras from Slovenia (village of Socka, north of Celje; Sava folds in Central Slovenia) and Croatia (Central Dalmatia – Mt Promina). One of the most important problems presented by the determination of individual species of fossil leaves is connected with the complex classification (species, genus and family) of traditional determinations of architecture and leaf morphology and also of cuticular studies. In this case, the problems are related to the determination of some fossil leaves and the morphological similarities inside some families, genera or species and among some families. This is related to conifers (Cupressaceae, Taxodiaceae, Araucariaceae), laurels (similarities among themselves and between some families), the families Myricaceae, Moraceae, Rhamnaceae, Proteaceae, Sapotaceae and »Leguminosae« type of leaves. In spite of these problems general palaeobotanical conclusions are very close to composition of classic Palaeogene palaeo-phytoassociations.Članak ističe složenost determiniranja i taksonomsku problematiku uzoraka fosilne makroflore iz Socke i Posavskih bora (Slovenija) i šire okoline planine Promine (Hrvatska). Posebice je izražena problematika određivanja pojedinačnih uzoraka i njihovo pravilno svrstavanje (vrsta, rod, porodica), no unatoč svemu ne remeti se zaključak o ukupnom sastavu i karakteru fosilnih biljnih zajednica toga doba. Ovdje se ističe problematika određivanja pojedinih vrsta i njihove međusobne morfološke sličnosti, kako unutar samih porodica, rodova i vrsta, tako i između pojedinih vrsta. To se odnosi na fosilne četinjače (Cupressaceae, Taxodiaceae, Araucariaceae), lovore (međusobne sličnosti i sličnosti pojedinim drugim porodicama), porodice Myricaceae, Moraceae, Rhamnaceae, Proteaceae, Sapotaceae i lišće tzv. »leguminoznoga tipa«

Experimental observation of the spin-Hall effect in a two dimensional spin-orbit coupled semiconductor system

We report the experimental observation of the spin-Hall effect in a two-dimensional (2D) hole system with Rashba spin-orbit coupling. The 2D hole layer is a part of a p-n junction light-emitting diode with a specially designed co-planar geometry which allows an angle-resolved polarization detection at opposite edges of the 2D hole system. In equilibrium the angular momenta of the Rashba split heavy hole states lie in the plane of the 2D layer. When an electric field is applied across the hole channel a non zero out-of-plane component of the angular momentum is detected whose sign depends on the sign of the electric field and is opposite for the two edges. Microscopic quantum transport calculations show only a weak effect of disorder suggesting that the clean limit spin-Hall conductance description (intrinsic spin-Hall effect) might apply to our system.Comment: 4 pages, 3 figures, paper based on work presented at the Gordon Research Conference on Magnetic Nano-structures (August 2004) and Oxford Kobe Seminar on Spintronics (September 2004); accepted for publication in Physical Review Letters December 200

Effect of inversion asymmetry on the intrinsic anomalous Hall effect in ferromagnetic (Ga,Mn)As

The relativistic nature of the electron motion underlies the intrinsic part of the anomalous Hall effect, believed to dominate in ferromagnetic (Ga,Mn)As. In this paper, we concentrate on the crystal band structure as an important facet to the description of this phenomenon. Using different k.p and tight-binding computational schemes, we capture the strong effect of the bulk inversion asymmetry on the Berry curvature and the anomalous Hall conductivity. At the same time, we find it not to affect other important characteristics of (Ga,Mn)As, namely the Curie temperature and uniaxial anisotropy fields. Our results extend the established theories of the anomalous Hall effect in ferromagnetic semiconductors and shed new light on its puzzling nature

Coherent control of magnetization precession in ferromagnetic semiconductor (Ga,Mn)As

We report single-color, time resolved magneto-optical measurements in ferromagnetic semiconductor (Ga,Mn)As. We demonstrate coherent optical control of the magnetization precession by applying two successive ultrashort laser pulses. The magnetic field and temperature dependent experiments reveal the collective Mn-moment nature of the oscillatory part of the time-dependent Kerr rotation, as well as contributions to the magneto-optical signal that are not connected with the magnetization dynamics.Comment: 6 pages, 3 figures, accepted in Applied Physics Letter

Paleogenska fosilna flora Slovenije, Hrvatske i Bosne i Hercegovine

Localities with Paleogene flora are situated in the NE and Central Slovenia, Istria and Central Dalmatia (Croatia) and SW Herzegovina (Bosnia and Herzegovina). Taxa are arranged in 87 families, 214 genera and 496 different species. Without doubt the composition of the paleo-phytoassociations indicates the paleotropic character of the determined flora (tropical-sub-tropical elements, holarctic elements, cosmopolitan and southern hemisphere elements). It was possible to position each locality in an adequate floristic complex: the localities Raša (Istria), Mt. Promina (Dalmatia) and those in the Herzegovina are situated in the Mediterranean Tethys bioprovince – Raša, Mt., Promina NW Herzegovina = Montebolca flororistic complex; Mt. Promina and NW Herzegovina also = Célas floristic complex. The locality Socka, and localities situated in the Sava folds are a part of the trans-European Paratethys bioprovince – Socka = Lábatlan floristic complex; Sava folds (Zagorje, Trbovlje, Novi Dol) = Kiscell floristic complex.Lokaliteti s paleogenskom florom smješteni su u SI i središnjem dijelu Slovenije, Istri, središnjoj Dalmaciji, te u SZ Hercegovini. Taksoni su svrstani u 87 porodica, 214 rodova i 496 različitih vrsta. Sastav paleofitozajednica bez sumnje upućuje na paleotropski karakter determinirane flore (tropsko-suptropski elementi, holarktički elementi, kozmopolitski i elementi južne hemisfere). Svaki se lokalitet može smjestiti u odgovarajući floristički kompleks: Raša u Istri, lokaliteti Promine i onih u Hercegovini smješteni su u Sredozemnu tetijsku bioprovinciju (Raša, Promina, SZ Hercegovina = Montebolca floristički kompleks, a Promina i SZ Hercegovina djelimice imaju još i elemente Célas florističkog kompleksa). Lokalitet Socka i lokaliteti Posavskih bora bili su dijelovi Transeuropske paratetijske bioprovincije (Socka = Lábatlan floristički kompleks; Posavske bore /Zagorje, Trbovlje, Novi Dol/ = Kiscell floristički kompleks)

Povijest paleobotanickih istrazivanja u Hrvatskoj (in Croatian)

Ovim člankom autor je ukratko dao pregled paleobotaničkih istraživanja makroflore na tlu Hrvatske