다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

We present a review of experimental and theoretical studies of the anomalous Hall effect (AHE), focusing on recent developments that have provided a more complete framework for understanding this subtle phenomenon and have, in many instances, replaced controversy by clarity. Synergy between experimental and theoretical work, both playing a crucial role, has been at the heart of these advances. On the theoretical front, the adoption of Berry-phase concepts has established a link between the AHE and the topological nature of the Hall currents which originate from spin-orbit coupling. On the experimental front, new experimental studies of the AHE in transition metals, transition-metal oxides, spinels, pyrochlores, and metallic dilute magnetic semiconductors, have more clearly established systematic trends. These two developments in concert with first-principles electronic structure calculations, strongly favor the dominance of an intrinsic Berry-phase-related AHE mechanism in metallic ferromagnets with moderate conductivity. The intrinsic AHE can be expressed in terms of Berry-phase curvatures and it is therefore an intrinsic quantum mechanical property of a perfect cyrstal. An extrinsic mechanism, skew scattering from disorder, tends to dominate the AHE in highly conductive ferromagnets. We review the full modern semiclassical treatment of the AHE together with the more rigorous quantum-mechanical treatments based on the Kubo and Keldysh formalisms, taking into account multiband effects, and demonstrate the equivalence of all three linear response theories in the metallic regime. Finally we discuss outstanding issues and avenues for future investigation.

/pdf/anomalous-hall-effect-tyeyld308t.pdf

Anomalous hall effect

日本物理学会誌及びJournal of the Physical Society of Japanの月刊について

In solid-state materials with strong relativistic spin-orbit coupling, charge currents generate transverse spin currents. The associated spin Hall and inverse spin Hall effects distinguish between charge and spin current where electron charge is a conserved quantity but its spin direction is not. This review provides a theoretical and experimental treatment of this subfield of spintronics, beginning with distinct microscopic mechanisms seen in ferromagnets and concluding with a discussion of optical-, transport-, and magnetization-dynamics-based experiments closely linked to the microscopic and phenomenological theories presented.

Spin Hall effects

Annual review of condensed matter physics

The structure and magnetic behavior of hybrid films composed of maghemite (γ-Fe2O3) nanoparticles (NPs) and an asymmetric diblock copolymer (DBC) polystyrene61-block-polyN-isopropylacrylamide115 are investigated. The NPs are coated with PS chains, which allow for a selective incorporation inside the PS domains at different NP concentrations. Upon incorporation of low amounts of NPs into the DBC thin films, the initial parallel (to film surface) cylinder morphology changes to a well ordered, perpendicularly oriented one. The characteristic domain distance of the DBC is increased due to the swelling of the PS domains with NPs. At higher NP concentrations, the excess NPs which can no longer be embedded in the PS domains, are accumulated at the film surface, and NP aggregates form. Irrespective of NP concentration, a superparamagnetic behavior of the metal oxide-DBC hybrid films is found. Such superparamagnetic properties make the established hybrid films interesting for high density magnetic storage media and thermoresponsive magnetic sensors.

/pdf/arrangement-of-maghemite-nanoparticles-via-wet-chemical-self-22kg4mzixb.pdf

Arrangement of Maghemite Nanoparticles via Wet Chemical Self-Assembly in PS-b-PNIPAM Diblock Copolymer Films

The integration of ferromagnetic and ferroelectric materials into hybrid heterostructures yields multifunctional systems with improved or novel functionality. We here report on the structural, electronic and magnetic properties of the ferromagnetic double perovskite Sr2CrReO6, grown as epitaxial thin film onto ferroelectric BaTiO3. As a function of temperature, the crystal-structure of BaTiO3 undergoes phase transitions, which induce qualitative changes in the magnetic anisotropy of the ferromagnet. We observe abrupt changes in the coercive field of up to 1.2T along with resistance changes of up to 6.5%. These results are attributed to the high sensitivity of the double perovskites to mechanical deformation.

Giant magnetic anisotropy changes in Sr2CrReO6 thin films on BaTiO3

The wide bandgap semiconductor ZnO is interesting for spintronic applications because of its small spin-orbit coupling implying a large spin coherence length. Utilizing vertical spin valve devices with ferromagnetic electrodes (TiN/Co/ZnO/Ni/Au), we study the spin-polarized transport across ZnO in all-electrical experiments. The measured magnetoresistance agrees well with the prediction of a two spin channel model with spin-dependent interface resistance. Fitting the data yields spin diffusion lengths of 10.8 nm (2 K), 10.7 nm (10 K), and 6.2 nm (200 K) in ZnO, corresponding to spin lifetimes of 2.6 ns (2 K), 2.0 ns (10 K), and 31 ps (200 K).

Spin transport and spin dephasing in zinc oxide

We discuss the use of thin film heterostructures for the generation of artificial multiferroic or magnetoelectric material systems. In this regard the transition metal oxides BiFeO3 and BiCrO3 are of particular interest. By using laser molecular beam epitaxy we have grown epitaxial thin films of these materials on SrTiO3 substrates in a two-dimensional layer-by-layer growth mode. The films show small surface roughness and excellent crystallographic quality with mosaic spread below 0.04°. In contrast to the bulk materials, both BiFeO3 and BiCrO3 films have tetragonal crystal structure due to epitaxial coherency strain. The magnetic properties have been studied by SQUID magnetometry. In contrast to a previous report on BiFeO3 we find only a small saturation magnetization below 0.05μ B/formula unit both for BiFeO3 and BiCrO3, which can be explained by a canting of the antiferromagnetically aligned Fe and Cr spins, respectively. Furthermore, no indication for a strain induced enhancement of magnetization was ...

Multiferroic materials based on artificial thin film heterostructures

We study the magnetoresistance properties of thin ferromagnetic CrO2 and Fe3O4 films under microwave irradiation. Both the sheet resistance ? and the Hall voltage VHall characteristically change when a ferromagnetic resonance (FMR) occurs in the film. The electrically detected ferromagnetic resonance (EDFMR) signals closely match the conventional FMR, measured simultaneously, in both resonance fields and line shapes. The sign and the magnitude of the resonant changes ??/? and ?VHall/VHall can be consistently described in terms of a Joule heating effect. Bolometric EDFMR thus is a powerful tool for the investigation of magnetic anisotropy and magnetoresistive phenomena in ferromagnetic micro- or nanostructures.

/pdf/electrically-detected-ferromagnetic-resonance-3zly2a1pnh.pdf

Matthias Opel

Papers

Arrangement of Maghemite Nanoparticles via Wet Chemical Self-Assembly in PS-b-PNIPAM Diblock Copolymer Films

Giant magnetic anisotropy changes in Sr2CrReO6 thin films on BaTiO3

Spin transport and spin dephasing in zinc oxide

Multiferroic materials based on artificial thin film heterostructures

Electrically detected ferromagnetic resonance