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There is a growing interest in mixing spintronics and superconductivity to develop original energy-efficient nonvolatile memory and logic devices. Research works conducted so far have mostly focused on superconductor with critical temperature Tc lower than 10 K. Here, we report on the growth and characterization of MgB2/Ni80Fe20 and MgB2/Co bilayers, where Tc of the MgB2 layer is of the order of 30 K. Ferromagnetic resonance was undertaken to analyze the spin pumping into MgB2. The larger magnetization at saturation in Co, as compared to Ni80Fe20, induces a smaller spin pumping contribution to the damping when MgB2 is normal. A spin pumping reduction was observed for both bilayers when MgB2 becomes superconductor and is attributed to the opening of the superconducting gap. The present results show that MgB2 thin films could be suitable to implement superconducting spintronic at 30 K, which is not only relevant for future technological development but also relaxes experimental constraints related to low-temperature investigations. [ABSTRACT FROM AUTHOR]

We have studied the thermal variation of the switching field of magnetic islands at room temperature. A model bit-pattern media composed of an assembly of islands with 80 nm width was fabricated by sputter deposition onto a pre-patterned substrate. Using direct magnetic-contrast imaging of the islands under applied field, we extract the switching probabilities of individual islands. Based on an analytical model for the thermally activated switching of the islands, we are able to determine the intrinsic magnetic anisotropy of each island and, consequentially, a distribution of anisotropies for the island ensemble investigated. In the distribution, we identify a separated group of islands with a particularly small anisotropy. We attribute this group to islands containing misaligned grains triggering the magnetic reversal. At room temperature and slow field sweep rates, the observed thermal broadening of the switching-field distribution is small compared to the intrinsic broadening. However, we illustrate that thermal fluctuations play a crucial role at high sweep rates by extrapolating our results to technological relevant regimes. [ABSTRACT FROM AUTHOR]

The field-induced magnetic configurations in a [Co/Pd]15/TbFeCo exchange-spring system with perpendicular magnetic anisotropy are studied using torque magnetometry. The experimental results are compared to a 1D micromagnetic simulation. The good agreement between experiments and simulations allows us to deduce the evolution of the in-depth magnetic configuration as a function of the applied field orientation and amplitude. The chirality transition of the interfacial domain wall developing in the structure can also be determined with this technique. [ABSTRACT FROM AUTHOR]

Magnetic and magneto-transport properties of amorphous Al2O3-based magnetic tunnel junctions (MTJ) having two Co/Ni multilayer electrodes exhibiting perpendicular magnetic anisotropy (PMA) are presented. An additional Co/Pt multilayer is required to maintain PMA in the top Co/Ni electrode. Slight stacking variations lead to dramatic magnetic changes due to dipolar interactions between the top and bottom electrodes. Tunnel magneto-resistance (TMR) of up to 8% at 300K is measured for the MTJ with two PMA electrodes. The TMR value increases when the top PMA electrode is replaced by an in-plane magnetized Co layer. These observations can be attributed to significant intermixing in the top Co/Ni electrode. [ABSTRACT FROM AUTHOR]

The strong impact of molecular beam epitaxy growth and Synchrotron Radiation characterization tools in the understanding of fundamental issues in nanomagnetism and spintronics is illustrated through the example of fully epitaxial MgO-based Magnetic Tunnel Junctions (MTJs). If ab initio calculations predict very high tunnel magnetoresistance (TMR) in such devices, some discrepancy between theory and experiments still exists. The influence of imperfections in real systems has thus to be considered like surface contaminations, structural defects, unexpected electronic states, etc. The influence of possible oxygen contamination at the Fe/MgO(001) interface is thus studied, and is shown to be not so detrimental to TMR as predicted by ab initio calculations. On the contrary, the decrease of dislocations density in the MgO barrier of MTJs using Fe1-xVx electrodes is shown to significantly increase TMR. Finally, unexpected transport properties in Fe1-XCox/MgO/ Fe1-XCox (001) are presented. With the help of spin and symmetry resolved photoemission and ab initio calculation, the TMR decrease for Co content higher than 25% is shown to come from the existence of an interface state and the shift of the empty D1 minority spin state towards the Fermi level. [ABSTRACT FROM AUTHOR]

We present an experimental and theoretical study of Pauli paramagnetism and martensite stabilization in a near equiatomic NiTi shape memory alloy. We demonstrate a direct correlation between strain-induced shear of the B19′ NiTi lattice and its electronic and thermodynamical features. An increase in the monoclinic angle β from 97.4 to 98° induces a 7% decrease in the magnetic susceptibility because of a shift and deepening of a dip in B19′ density of states at the Fermi level. It also produces a decrease in the B19′ enthalpy, which translates into an increase in the martensite-to-austenite transition temperature by 60 K. [ABSTRACT FROM AUTHOR]

1. Introduction Experimental models have accelerated our understanding of diseases' pathophysiology and played a major role in the search for adequate therapeutic interventions. Ischemia reperfusion injury (IRI) remains a leading [...], Animal experimentation is necessary to characterize human diseases and design adequate therapeutic interventions. In renal transplantation research, the limited number of in vitro models involves a crucial role for in vivo models and particularly for the porcine model. Pig and human kidneys are anatomically similar (characterized by multilobular structure in contrast to rodent and dog kidneys unilobular). The human proximity of porcine physiology and immune systems provides a basic knowledge of graft recovery and inflammatory physiopathology through in vivo studies. In addition, pig large body size allows surgical procedures similar to humans, repeated collections of peripheral blood or renal biopsies making pigs ideal for medical training and for the assessment of preclinical technologies. However, its size is also its main drawback implying expensive housing. Nevertheless, pig models are relevant alternatives to primate models, offering promising perspectives with developments of transgenic modulation and marginal donor models facilitating data extrapolation to human conditions.

Strain modulation during a two-way shape memory effect (TWSME) in a sputtered nitinol NiTi is used to reliably induce and switch by 90° a uniaxial magnetic anisotropy of a 20 nm thick Ni film during the thermal cycle from 300 K to 400 K. NiTi strain and its distribution are carefully measured by digital image correlation during tensile prestrain and subsequent temperature cycles in order to compare with Ni strain extracted from the magnetometry measurement and from transmission electron microscopy. In a NiTi/Ni bilayer, a variation of 2.7% strain in NiTi during the TWSME generates 1.3% strain in Ni, which results in a transition from −2 × 104 J/m3 in-plane magnetic anisotropy to +1 × 105 J/m3. Such a composite system offers a way to timely ease writability while maintaining high thermal stability at rest in magnetic media. [ABSTRACT FROM AUTHOR]

Despite the fact that a significant fraction of kidney graft dysfunctions observed after transplantation is due to ischemia-reperfusion injuries, there is still no clear consensus regarding optimal kidney preservation strategy. This stems directly from the fact that as of yet, the mechanisms underlying ischemia reperfusion injury are poorly defined, and the role of each preservation parameter is not clearly outlined. In the meantime, as donor demography changes, organ quality is decreasing which directly increases the rate of poor outcome. This situation has an impact on clinical guidelines and impedes their possible harmonization in the transplant community, which has to move towards changing organ preservation paradigms: new concepts must emerge and the definition of a new range of adapted preservation method is of paramount importance. This review presents existing barriers in transplantation (e.g., temperature adjustment and adequate protocol, interest for oxygen addition during preservation, and clear procedure for organ perfusion during machine preservation), discusses the development of novel strategies to overcome them, and exposes the importance of identifying reliable biomarkers to monitor graft quality and predict short and long-term outcomes. Finally, perspectives in therapeutic strategies will also be presented, such as those based on stem cells and their derivatives and innovative models on which they would need to be properly tested. [ABSTRACT FROM AUTHOR]

We describe the results of adding a new biological agent HEMO2life® to a standard preservation solution for hypothermic static lung preservation aiming to improve early functional parameters after lung transplantation. HEMO2life® is a natural oxygen carrier extracted from Arenicola marina with high oxygen affinity developed as an additive to standard organ preservation solutions. Standard preservation solution (Perfadex®) was compared with Perfadex® associated with HEMO2life® and with sham animals after 24 h of hypothermic preservation followed by lung transplantation. During five hours of lung reperfusion, functional parameters and biomarkers expression in serum and in bronchoalveolar lavage fluid (BALF) were measured. After five hours of reperfusion, HEMO2life® group led to significant improvement in functional parameters: reduction of graft vascular resistance (p < .05) and increase in graft oxygenation ratio (p < .05). Several ischemia-reperfusion related biomarkers showed positive trends in the HEMO2life® group: expression of HMG B1 in serum tended to be lower in comparison (2.1 ± 0.8 vs. 4.6 ± 1.5) with Perfadex® group, TNF-α and IL-8 in BALF were significantly higher in the two experimental groups compared to control (p < .05). During cold ischemia, expression of HIF1α and histology remained unchanged and similar to control. Supplementation of the Perfadex® solution by an innovative oxygen carrier HEMO2life® during hypothermic static preservation improves early graft function after prolonged cold ischemia in lung transplantation. [ABSTRACT FROM AUTHOR]

We report on the magnetization at the Cr/MgO interface, which we studied through two complementary techniques: angle-resolved photoemission spectroscopy and polarized neutron reflectivity. We experimentally observe an enhanced interface magnetization at the interface, yet with values much smaller than the ones reported so far by theoretical and experimental studies on Cr(001) surfaces. Our findings cast some doubts on the interpretations on previous works and could be useful in antiferromagnetic spin torque studies. [ABSTRACT FROM AUTHOR]

Interplay between voltage-induced magnetic anisotropy transition and voltage-induced atomic diffusion is studied in epitaxial V/Fe (0.7 nm)/ MgO/ Fe(5 nm)/Co/Au magnetic tunnel junction where thin Fe soft electrode has in-plane or out-of-plane anisotropy depending on the sign of the bias voltage. We investigate the origin of the slow resistance variation occurring when switching bias voltage in opposite polarity. We demonstrate that the time to reach resistance stability after voltage switching is reduced when increasing the voltage amplitude or the temperature. A single energy barrier of about 0.2 eV height is deduced from temperature dependence. Finally, we demonstrate that the resistance change is not correlated to a change in soft electrode anisotropy. This conclusion contrasts with observations recently reported on analogous systems. [ABSTRACT FROM AUTHOR]

We demonstrate the ability to create, control the propagation, and annihilate domain walls in 25- nm thick Tb22Co78 ferrimagnetic alloy wires using a temperature gradient under a constant applied field. The temperature gradient is generated by passing a current through the wire, and the domain wall properties are imaged using Kerr microscopy. The manipulation of the domain wall is made possible by creating a temperature gradient such that the temperature at one end of the wire is above the compensation temperature for the TbCo alloy, while the other end remains below the compensation temperature. By tuning the intensity of the applied magnetic field and the current flowing inside the wire, it is possible to carefully control the domain wall position that can then be stabilized under zero applied field and current. [ABSTRACT FROM AUTHOR]

Field-induced magnetization dynamics in a [Co/Ni] superlattice exhibiting strong perpendicular magnetic anisotropy is studied using Kerr microscopy. We report domain wall velocity over 8 decades within thermally activated, transitory, and flow dynamical regimes. At low field, the thermally activated regime is characterized by dendritic domain growth that differs from the creep mechanism usually observed for the interaction of domains wall with a 2D random pinning potential for layers grown by sputtering. This result is explained by the epitaxial nature of the [Co/Ni] superlattices involving a single-type defect. The transition from the thermally activated to the flow regime is characterized by a reduction of the density of non-reversed domains which exists after domain wall displacement. [ABSTRACT FROM AUTHOR]

Extraordinary Hall Effect (EHE) based original concepts of a reconfigurable logic gate and a multibit logic comparator are presented. They exploit the EHE voltage that develops on cross cells connected in series that has no size limitation down to the nanometer scale. Experimental demonstrations are performed on both micro- and nanometer lateral size crosses made of ferrimagnetic TbCo alloy. The simplicity of the device architecture and its robustness make it advantageous when compared with existing systems. [ABSTRACT FROM AUTHOR]

Using a direct imaging method, we experimentally investigate the reversal of magnetic islands in a bit-patterned media sample based on a pre-patterned substrate. Due to systematic variation of the island distances in the media, we are able to study the influence of the dipolar interaction on the switching-field distribution of the island ensemble. The experimental findings are explained by an analytical magnetostatic model that allows us to quantify the different components of the demagnetizing field in the system and to distinguish intrinsic and dipolar broadening of the switchingfield distribution. Besides the well-known dipolar broadening due to stray fields from neighboring islands, we find strong influence from the magnetized trench material on the island switching. [ABSTRACT FROM AUTHOR]

Wefabricatedaperpendicularlymagnetizedbitpatternmediausingahexagonallyclose-packed auto-assembled anodic alumina template with 100 nm and 50 nm periods by depositing a Co/Pt multilayer toform an ordered array of ferromagnetic nanodots, so-called nanobumps. We used Hall resistance measurements and magnetic force microscopy to characterize the dot-by-dot magnetization reversal mechanism under applied field The role of interdot exchange coupling and dipolar coupling are investigated. Then we focus on separating the various origins of switching field distribution (SFD) in this system, namely dipolar interactions, intrinsic anisotropy distribution, and template packing faults. Finally we discuss the influence of triangular dipolar frustrations on the energy stability of demagnetized and half-switched states based on an Ising model, including local exchange coupling. The impact of SFD and lattice defects lines between misoriented ordered domains on the magnetic configurations is studied in detail. [ABSTRACT FROM AUTHOR]

We present a method to map the saturation magnetization of soft ultrathin films with perpendicular anisotropy, and we illustrate it to assess the compositional dependence of the magnetization of CoFeB(1 nm)/MgO films. The method relies on the measurement of the dipolar repulsion of parallel domain walls that define a linear domain. The film magnetization is linked to the field compressibility of the domain. The method also yields the minimal distance between two walls before their merging, which sets a practical limit to the storage density in spintronic devices using domain walls as storage entities. [ABSTRACT FROM AUTHOR]

Owing to their bcc structures and the low lattice misfit with MgO, FeV alloys are interesting for MgO-based magnetic tunnel junctions. We use vector network analyzer ferromagnetic resonance to measure the magnetization, anisotropy, exchange stiffness, and damping of epitaxial FeV/MgO thin alloys of various V contents. The low magnetization, very high exchange stiffness (23 pJ/m) and very low effective damping (<0.0026) of the alloy with 20% V content makes it an interesting candidate for spin torque applications. The ultralow damping is consistent with a spin-orbit origin, which sheds light on the possible strategies to reduce the damping in alloys. [ABSTRACT FROM AUTHOR]

Single-crystalline V/Fe(0.7 nm)/MgO(1.2nm)/Fe(20 nm) magnetic tunnel junctions are studied to quantify the influence of an electric field on the Fe/MgO interface magnetic anisotropy. The thinnest Fe soft layer has a perpendicular magnetic anisotropy (PMA), whereas the thickest Fe layer acts as sensor for magnetic anisotropy changes. When electrons are added at the PMA Fe/MgO interface (negative voltage), no anisotropy changes are observed. For positive voltage, the anisotropy constant decreases with increasing bias voltage. A huge 1150 fJ V-1 m-1 anisotropy variation with field is observed and the magnetization is found to turn from out-of-plane to in-plane of the sample with the applied voltage. [ABSTRACT FROM AUTHOR]

High-temperature (near Curie-point) magnetization-behavior in materials with strong-perpendicular-magnetocrystalline-anisotropy has recently gained importance due to potential applications in thermally/heat-assisted-magnetic-recording (TAR/HAMR) systems. We have implemented a macrospin-model within the Landau-Lifshitz-Bloch formalism for strongly exchange-coupled CoNi/Pd multilayers subject to nanosecond-scale localized-heat and magnetic-field pulses. The temperature dependence of the longitudinal-susceptibility, as determined from a single-fitting-parameter of the experimental coercive-field, is consistent with the previously reported ab initio calculations. We demonstrate that this model is able to predict the full map of switching-speed as a function of magnetic-field and local-temperature providing a robust tool for the evaluation of this and similar material systems in TAR/HAMR applications. [ABSTRACT FROM AUTHOR]

In combining spin- and symmetry-resolved photoemission, magnetotransport measurements and ab initio calculations we detangled the electronic states involved in the electronic transport in Fe1-xCox(001)/MgO/Fe1-xCox(001) magnetic tunnel junctions. Contrary to previous theoretical predictions, we observe a large reduction in TMR (from 530 to 200% at 20 K) for Co content above 25 atomic % as well as anomalies in the conductance curves. We demonstrate that these unexpected behaviors originate from a minority spin state with Δ1 symmetry that exists below the Fermi level for high Co concentration. Using angle-resolved photoemission, this state is shown to be a two-dimensional state that occurs at both Fe1-xCox(001) free surface, and more importantly at the interface with MgO. The combination of this interface state with the peculiar density of empty states due to chemical disorder allows us to describe in details the complex conduction behavior in this system. [ABSTRACT FROM AUTHOR]

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