Anisotropic charge dynamics in the quantum spin-liquid candidate κ\kappa-(BEDT-TTF)2_2Cu2_2(CN)3_3

We have in detail characterized the anisotropic charge response of the dimer Mott insulator $\kappa$-(BEDT-TTF)$_2$\-Cu$_2$(CN)$_3$ by dc conductivity, Hall effect and dielectric spectroscopy. At room temperature the Hall coefficient is positive and close to the value expected from stoichiometry; the temperature behavior follows the dc resistivity $\rho(T)$. Within the planes the dc conductivity is well described by variable-range hopping in two dimensions; this model, however, fails for the out-of-plane direction. An unusually broad in-plane dielectric relaxation is detected below about 60 K; it slows down much faster than the dc conductivity following an Arrhenius law. At around 17 K we can identify a pronounced dielectric anomaly concomitantly with anomalous features in the mean relaxation time and spectral broadening. The out-of-plane relaxation, on the other hand, shows a much weaker dielectric anomaly; it closely follows the temperature behavior of the respective dc resistivity. At lower temperatures, the dielectric constant becomes smaller both within and perpendicular to the planes; also the relaxation levels off. The observed behavior bears features of relaxor-like ferroelectricity. Because heterogeneities impede its long-range development, only a weak tunneling-like dynamics persists at low temperatures. We suggest that the random potential and domain structure gradually emerge due to the coupling to the anion network.Comment: 14 pages, 13 figure

Switching the magnetic configuration of a spin valve by current induced domain wall motion

We present experimental results on the displacement of a domain wall by injection of a dc current through the wall. The samples are 1 micron wide long stripes of a CoO/Co/Cu/NiFe classical spin valve structure. The stripes have been patterned by electron beam lithography. A neck has been defined at 1/3 of the total length of the stripe and is a pinning center for the domain walls, as shown by the steps of the giant magnetoresistance curves at intermediate levels (1/3 or 2/3) between the resistances corresponding to the parallel and antiparallel configurations. We show by electric transport measurements that, once a wall is trapped, it can be moved by injecting a dc current higher than a threshold current of the order of magnitude of 10^7 A/cm^2. We discuss the different possible origins of this effect, i.e. local magnetic field created by the current and/or spin transfer from spin polarized current.Comment: 3 pages, 3 figure

Anomalous Hall effect and weak localization corrections in a ferromagnet

In this paper, we report results on the anomalous Hall effect. First, we summarize analytical calculations based on the Kubo formalism : explicit expressions for both skew-scattering and side-jump are derived and weak-localization corrections are discussed. Next, we present numerical calculations of the anomalous Hall resistivity based on the Dirac equation. Qualitative agreement with experiments is obtained.Comment: Proceeding JEMS'0

Extrinsic Spin Hall Effect Induced by Iridium Impurities in Copper

We study the extrinsic spin Hall effect induced by Ir impurities in Cu by injecting a pure spin current into a CuIr wire from a lateral spin valve structure. While no spin Hall effect is observed without Ir impurity, the spin Hall resistivity of CuIr increases linearly with the impurity concentration. The spin Hall angle of CuIr, $(2.1 \pm 0.6)$% throughout the concentration range between 1% and 12%, is practically independent of temperature. These results represent a clear example of predominant skew scattering extrinsic contribution to the spin Hall effect in a nonmagnetic alloy.Comment: 5 pages, 4 figure

Clinical analysis of etiology, risk factors and outcome in patients with acute kidney injury.

Acute kidney injury is characterized by a rapid loss of renal excretory function with the increase of nitrogen compounds in the blood and with different outcome. Objective: Since descriptions of the risk factors and sequelae of acute kidney injury (AKI) remain relatively limited, the objective of this study was to determine etiology and clinical characteristics of AKI, as well as risk factors for adverse outcome of renal function and death in AKI patients. Methods: We retrospectively studied a cohort of 84 adult AKI patients admitted to Nephrology Clinic in University Clinical Centre Sarajevo during period 2012-2014. Demographic, laboratory and clinical parameters were retrieved. The in-hospital and 6 months mortality were recorded. Renal function outcome was defined 3 months following discharge. Results: Majority of patients were older (median age 73.5 years) with great severity of AKI (Stage III in 78.5% of cases) and high burden of comorbidities (mean Charlson comorbidity index, CCI score 6.4±3.05). The most common causes of AKI were acute interstitial nephritis (16.7%), heart failure (15.5%), gastroenterocolitis (13.1%), and sepsis (12%). Renal function recovery was recorded in 48.8% of patients, with prevalence of 10.7% of intrahospital mortality and 37.3% of 6 months mortality. Risk factors for poor outcome of renal function and mortality in AKI patients were increasing age and higher CCI score, while protective factor was higher diuresis. Sepsis proved to be risk factor for deat

Hall effect in the heavy-fermion compound CePtSi

We present Hall-effect measurements on the heavy-fermion compound CePtSi. Above the temperature of antiferromagnetic ordering T_N, the Hall effect of CePtSi exhibits the behavior generally observed in heavy-fermion systems and ascribed to skew scattering. Below T_N the Hall effect is enhanced and its field dependence is strongly nonlinear. We show that this behavior arises from skew scattering or anomalous velocity effects rather than from a change of the ordinary Hall effect induced by a reconstruction of the Fermi surface

Co-doped (La,Sr)TiO3-d: a high-Curie temperature diluted magnetic system with large spin-polarization

We report on tunneling magnetoresistance (TMR) experiments that demonstrate the existence of a significant spin polarization in Co-doped (La,Sr)TiO3-d (Co-LSTO), a ferromagnetic diluted magnetic oxide system (DMOS) with high Curie temperature. These TMR experiments have been performed on magnetic tunnel junctions associating Co-LSTO and Co electrodes. Extensive structural analysis of Co-LSTO combining high-resolution transmission electron microscopy and Auger electron spectroscopy excluded the presence of Co clusters in the Co-LSTO layer and thus, the measured ferromagnetism and high spin polarization are intrinsic properties of this DMOS. Our results argue for the DMOS approach with complex oxide materials in spintronics

Full oxide heterostructure combining a high-Tc diluted ferromagnet with a high-mobility conductor

We report on the growth of heterostructures composed of layers of the high-Curie temperature ferromagnet Co-doped (La,Sr)TiO3 (Co-LSTO) with high-mobility SrTiO3 (STO) substrates processed at low oxygen pressure. While perpendicular spin-dependent transport measurements in STO//Co-LSTO/LAO/Co tunnel junctions demonstrate the existence of a large spin polarization in Co-LSTO, planar magnetotransport experiments on STO//Co-LSTO samples evidence electronic mobilities as high as 10000 cm2/Vs at T = 10 K. At high enough applied fields and low enough temperatures (H < 60 kOe, T < 4 K) Shubnikov-de Haas oscillations are also observed. We present an extensive analysis of these quantum oscillations and relate them with the electronic properties of STO, for which we find large scattering rates up to ~ 10 ps. Thus, this work opens up the possibility to inject a spin-polarized current from a high-Curie temperature diluted oxide into an isostructural system with high-mobility and a large spin diffusion length.Comment: to appear in Phys. Rev.