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Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, los autores pertenecientes a la UAM y el nombre del grupo de colaboración, si lo hubiere, We present the design, fabrication, and characterization of an implantable neural interface based on anisotropic magnetoresistive (AMR) magnetic-field sensors that combine reduced size and high performance at body temperature. The sensors are based on La0.67Sr0.33MnO3 (LSMO) as a ferromagnetic material, whose epitaxial growth has been suitably engineered to get uniaxial anisotropy and large AMR output together with low noise even at low frequencies. The performance of LSMO sensors of different film thickness and at different temperatures close to 37 °C has to be explored to find an optimum sensitivity of ∼400%/T (with typical detectivity values of 2 nT·Hz-1/2 at a frequency of 1 Hz and 0.3 nT·Hz-1/2 at 1 kHz), fitted for the detection of low magnetic signals coming from neural activity. Biocompatibility tests of devices consisting of submillimeter-size LSMO sensors coated by a thin poly(dimethyl siloxane) polymeric layer, both in vitro and in vivo, support their high suitability as implantable detectors of low-frequency biological magnetic signals emerging from heterogeneous electrically active tissues

Direct integration of ferroelectric Hf0.5Zr0.5O2 (HZO) on the inert surface of graphene is challenging. Here, using nucleation layers to promote atomic layer deposition of HZO was investigated. Different metals were deposited as nucleation layers via dc sputtering. Ta, which oxidizes in air to form a sub-stoichiometric oxide, was compared to Pt, which offers a more stable electrode. For thicker interlayers, Ta leads to unstable switching behavior of the HZO film. Conversely, at smaller thicknesses, a higher Pr can be achieved with an oxidized Ta interlayer. In both cases, Pt offers higher endurance. The choice of interlayer may strongly depend on the required application.

Spin currents can modify the magnetic state of ferromagnetic ultrathin films through spin-orbit torque. They may be generated by means of spin-orbit interactions by either bulk or interfacial phenomena. Electrical transport measurements reveal a 6-fold increase of the spin-orbit torque accompanied by a drastic reduction of the spin Hall magnetoresistance upon the introduction of an ultrathin Cu interlayer in a Pt/Cu/Co/Pt structure with perpendicular magnetic anisotropy. We analyze the dependence of the spin Hall magnetoresistance with the thickness of the interlayer, ranging from 0.5 to 15 nm, in the frame of a drift diffusion model that provides information on the expected spin currents and spin accumulations in the system. The results demonstrate that the major responsibility of both effects is spin memory loss at the interface. The enhancement of the spin-orbit torque when introducing an interlayer opens the possibility to design more efficient spintronic devices based on materials that are cheap and abundant such as copper. More specifically, spin-orbit torque magnetic random access memories and spin logic devices could benefit from the spin-orbit torque enhancement and cheaper material usage presented in this study.

Recent advances on the stabilization and manipulation of chiral magnetization configurations in systems consisting in alternating atomic layers of ferromagnetic and non-magnetic materials hold promise of innovation in spintronics technology. The low dimensionality of the systems promotes spin orbit driven interfacial effects like antisymmetric Dzyaloshinskii-Moriya interactions (DMI) and surface magnetic anisotropy, whose relative strengths may be tuned to achieve stable nanometer sized magnetic objects with fixed chirality. While in most of the cases this is obtained by engineering complex multilayers stacks in which interlayer dipolar fields become important, we consider here a simple epitaxial trilayer in which a ferromagnet, with variable thickness, is embedded between a heavy metal and graphene. The latter enhances the perpendicular magnetic anisotropy of the system, promotes a Rashba-type DMI, and can sustain very long spin diffusion length. We use a layer-resolved micromagnetic model (LRM) to describe the magnetization textures and their chirality. Our results demonstrate that for Co thickness larger than 3.6 nm, a skyrmion having an intrinsic mixed Bloch-N\'eel character with counter-clock-wise chirality is stabilized in the entire (single) Co layer. Noteworthy, for thicknesses larger than 5.4 nm, the skyrmion switches its chirality, from counter-clock-wise to clock-wise., Comment: 10 pages, 7 figures

International audience; The current trend in magnetoresistive sensors development is to increase the sensitivity of single sensing elements by using multilayer structures and to design them into arrays. Such arrays are designed to compensate the excess low frequency noise of individual elements, which limits their magnetic resolution. Here, we report the modeling, design, and fabrication of single layer anisotropic magnetoresistive (AMR) sensors using low noise epitaxial La2/3Sr1/3MnO3 (LSMO) oxide thin films deposited on vicinal SrTiO3 substrates. The fabrication process is simple, and the operation of the sensor is based on a step-induced uniaxial magnetic anisotropy, described using the Stoner–Wohlfarth model. A coherent magnetization reversal process is observed by magneto-optical Kerr effect imaging. A good agreement between experimental data and the expected sensor response confirms the correct operation of the device. Three main fabrication parameters, namely the vicinal angle of the substrate, the deposition temperature, the thin film thickness, and their effects on film anisotropy field and device detectivity have been studied. Detectivity levels as low as 1.4 nT Hz–1/2 at 1 Hz and 240 pT Hz–1/2 in the white noise region are achieved with a single Wheatstone bridge element operating at 310 K. Compared to GMR and AMR sensors, these results are promising for further development and for their use as single layer LSMO low field AMR sensors, including applications as implantable biomedical devices.

Understanding formation of metastable phases by rapid energy pumping and quenching has been intriguing scientists for a long time. This issue is crucial for technologically relevant systems such as magnetic skyrmions which are frequently metastable at zero field. Using Atomistic Spin Dynamics simulations, we show the possibility of creating metastable skyrmion lattices in cobalt-based trilayers by femtosecond laser heating. Similar to the formation of supercooled ice droplets in the gas phase, high temperature ultrafast excitation creates magnon drops and their fast relaxation leads to acquisition and quenching of the skyrmion topological protection. The interplay between different processes corresponds to a specific excitation window which can be additionally controlled by external fields. The results are contrasted with longer-scale heating leading to a phase transition to the stable states. Our results provide insight into the dynamics of the highly non-equilibrium pathway for spin excitations and pave additional routes for skyrmion-based information technologies.

The structural, electronic, and magnetic properties of Sr-hole-doped epitaxial La

Pain therapy for low back pain in pregnancy is a very topical issue. In fact, it is necessary to balance the patient’s needs to control pain with the need to manage a pregnancy without negative effects on the fetus. We report a case of a 37-year-old woman with low back pain treated with neurostimulation before pregnancy. She described severe chronic low back pain unresponsive to pharmacologic treatments. We first implanted a subcutaneous stimulator into the patient, and then a definitive stimulator resulting in excellent pain control. The improvement in her quality of life allowed the woman to become pregnant. We decided to stop neurostimulation with the patient during pregnancy. The patient completed her pregnancy without complications and the baby was born healthy. During the pregnancy, the woman took only paracetamol when needed. However, this painful symptomatology, completely anecdotal, is not attributable solely to the previous spine problem but probably also to the changes occurring during pregnancy. At the end of pregnancy, the neurostimulator was reactivated without any discomfort for the patient, who is now pain free. This case report provides a first line of evidence of a possible treatment of low back pain in women intending to become pregnant, with risk-free management for both the patient and the child.

Single-layer magnetoresistive sensors were designed in a Wheatstone bridge configuration using La_2/_3Sr_1/_3MnO_3 ferromagnetic oxide thin film. Uniaxial anisotropy was induced by performing epitaxial deposition of the films on top of vicinal SrTiO_3 substrate. X-ray scan confirms the high crystalline quality of the films and the magnetic anisotropy was checked by magneto-optical Kerr effect measurements. Thanks to the anisotropic magnetoresistive effect and the very low noise measured in the devices, sub-nT resolution was achieved above 100 Hz at 310 K.

Nanometer-thick epitaxial Co films intercalated between graphene (Gr) and a heavy metal (HM) substrate are promising systems for the development of spin–orbitronic devices due to their large perpendicular magnetic anisotropy (PMA). A combination of theoretical modeling and experiments reveals the origin of the PMA and explains its behavior as a function of the Co thickness. High quality epitaxial Gr/Con/HM(111) (HM = Pt,Ir) heterostructures are grown by intercalation below graphene, which acts as a surfactant that kinetically stabilizes the pseudomorphic growth of highly perfect Co face-centered tetragonal (fct) films, with a reduced number of stacking faults as the only structural defect observable by high-resolution scanning transmission electron microscopy (STEM). Magneto-optic Kerr effect (MOKE) measurements show that such heterostructures present PMA up to large Co critical thicknesses of about 4 nm (20 ML) and 2 nm (10 ML) for Pt and Ir substrates, respectively. X-ray magnetic circular dichroism (XMCD) measurements show an inverse power law of the anisotropy of the orbital moment with Co thickness, reflecting its interfacial nature, that changes sign at about the same critical values. First principles calculations show that, regardless of the presence of graphene, ideal Co fct films on HM buffers do not sustain PMAs beyond around 6 mLs due to the in-plane contribution of the inner bulk-like Co layers. The large experimental critical thicknesses sustaining PMA can only be retrieved by the inclusion of structural defects that promote a local hcp stacking such as twin boundaries or stacking faults. Remarkably, a layer resolved analysis of the orbital momentum anisotropy reproduces its interfacial nature, and reveals that the Gr/Co interface contribution is comparable to that of the Co/Pt(Ir)., Financial support from MINECO (Grant Nos. RTI2018-097895-B-C41, RTI2018-097895-B-C42 and RTI2018-097895-B-C43 (FUN-SOC), PID2019-103910GB-I00, FIS2016-78591-C3-1-R and FIS2016-78591-C3-2-R (SKYTRON), PGC2018-098613-B-C21 (SpOrQuMat), PCI2019-111908-2 and PCI2019-111867-2 (FLAGERA 3 grant SOgraphMEM)], from Regional Government of Madrid (grant number P2018/NMT-4321 (NANOMAGCOST-CM)) and from Gobierno Vasco-UPV/EHU (grant numbers GIU18/138 and IT-1246-19). We acknowledge experiments at ALBA BL29 via proposal no. 2019023333. IMDEA-Nanociencia acknowledges support from the “Severo Ochoa” Program for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686).

Interfacial proximity effects in antiferromagnetic/ferromagnetic (AFM/FM) bilayers control the exchange-bias (EB) phenomena exploited in most spintronic devices, although still is lack of full understanding. Discordant results, including different exchange-bias field (HE), coercivity (HC), or blocking temperature (TB) found even in similar systems, are usually ascribed to uncontrolled parameters, namely dissimilar interfacial defects, structure, and thicknesses. Here, it is shown in the very same sample that the magnetic domain structure during the magnetization reversal of the FM layer controls those mentioned effects. Simultaneous transport and vectorial-resolved magnetic measurements performed in a V2O3/Co system during warming after different field cooling (FC) procedures exhibit a strong dependence on the FC angle and the domain structure of the FM layer. Remarkably, magnetization reversal analysis reveals 35 K of variation in TB and up to a factor of two in HE. These observations can be explained within the random-field model for the interfacial exchange coupling with a fixed AFM domain structure in contact with a variable (angle-dependent) FM domain structure. The results highlight the importance of the domain structure and magnetization reversal of the FM layer (not previously considered) in the EB phenomena, with potential to tailor interfacial effects in future spintronic devices, This is a highly collaborative effort between IMDEA Nanociencia and UC San Diego. The authors thank C. Urban for help in the initial stages of this work. The sample fabrication and characterization were supported by the Department of Energy’s Office of Basic Energy Science, under grant # DE-FG02-87ER45332. The magnetic and transport measurements were supported by MINECO (Ministerio de Economía y Competitividad) (FIS2016-78591-C3-1-R, PGC2018-098613-B-C21, MAT2017-89960-R, RTI2018-097895-B-C42, PCI2019-111867-2, PID2020-116181RB-C31) and by Comunidad de Madrid Regional Government (NanomagCOST-CM, Ref. S2018/MIT-2850). J.M.D. acknowledges support from MINECO through the FPI program (BES-2017-080617). IMDEA-Nanociencia acknowledges support from the ‘Severo Ochoa’ Program for Centres of Excellence in R&D (MINECO Grants SEV-2016-0686, CEX2020-001039-S)

Although technologically challenging, the integration of ferroelectric thin films with graphene spintronics potentially allows the realization of highly efficient, electrically tuneable, non-volatile memories. Here, the atomic layer deposition (ALD) of ferroelectric Hf$_{0.5}$Zr$_{0.5}$O$_2$ (HZO) directly on graphene (Gr)/Co/heavy metal (HM) epitaxial stacks is investigated via the implementation of several nucleation methods. With an in-situ method employing an Al$_2$O$_3$ layer, the HZO demonstrates a remanent polarization (2Pr) of 19.2 $\mu C/cm^2$. An ex-situ, naturally oxidized sputtered Ta layer for nucleation produces a film with 2Pr of 10.81 $\mu C/cm^2$, but a lower coercive field over the stack and switching enduring over subsequent cycles. Magnetic hysteresis measurements taken before and after ALD deposition show strong perpendicular magnetic anisotropy (PMA), with only slight deviations in the magnetic coercive fields due to the HZO deposition process, thus pointing to a good preservation of the single-layer Gr. X-ray diffraction measurements further confirm that the high-quality interfaces demonstrated in the stack remain unperturbed by the ferroelectric deposition and anneal., Comment: Accepted at ACS Applied Materials & Interfaces

Taming the magnetic anisotropy of lanthanides through coordination environments is crucial to take advantage of the lanthanides properties in thermally robust nanomaterials. In this work, the electronic and magnetic properties of Dy-carboxylate metal–organic networks on Cu(111) based on an eightfold coordination between Dy and ditopic linkers are inspected. This surface science study based on scanning probe microscopy and X-ray magnetic circular dichroism, complemented with density functional theory and multiplet calculations, reveals that the magnetic anisotropy landscape of the system is complex. Surface-supported metal–organic coordination is able to induce a change in the orientation of the easy magnetization axis of the Dy coordinative centers as compared to isolated Dy atoms and Dy clusters, and significantly increases the magnetic anisotropy. Surprisingly, Dy atoms coordinated in the metallosupramolecular networks display a nearly in-plane easy magnetization axis despite the out-of-plane symmetry axis of the coordinative molecular lattice. Multiplet calculations highlight the decisive role of the metal–organic coordination, revealing that the tilted orientation is the result of a very delicate balance between the interaction of Dy with O atoms and the precise geometry of the crystal field. This study opens new avenues to tailor the magnetic anisotropy and magnetic moments of lanthanide elements on surfaces., The ALBA synchrotron is acknowledged for providing beam time at BOREAS beamline (proposal number 2015091454). This project has received funding from the European Research Council (ERC, grant 766555) and Marie Sklodowska-Curie Actions (MSCA, project 894924) under the European Union's Horizon 2020 research and innovation programme. This work has been financed by the Spanish Ministerio de Economía, Industria y Competitividad (projects FIS2016-78591-C3-1-R, RTI2018-097895-B-C42, MAT2016-78293-C6-2-R, MAT2017-85089-C2-1-R, and PID2019-107338RB-C65); the Comunidad de Madrid (Projects S2013/MIT-2850, P2018/NMT4321, and S2018/NMT-4367); the European Regional Development Fund (ERDF) under the program Interreg V-A España-Francia-Andorra (Contract No. EFA 194/16 TNSI); and “Severo Ochoa” Programme for Centres of Excellence in R&D (grants SEV-2016-0686, and SEV-2017-0706).

International audience; Spin Hall and Rashba–Edelstein effects, which are spin-to-charge conversion phenomena due to spin-orbit coupling (SOC), are attractingincreasing interest as pathways to manage rapidly and at low consumption cost the storage and processing of a large amount of data inspintronic devices as well as more efficient energy harvesting by spin-caloritronics devices. Materials with large SOC, such as heavy metals(HMs), are traditionally employed to get large spin-to-charge conversion. More recently, the use of graphene (gr) in proximity with largeSOC layers has been proposed as an efficient and tunable spin transport channel. Here, we explore the role of a graphene monolayer betweenCo and a HM and its interfacial spin transport properties by means of thermo-spin measurements. The gr/HM (Pt and Ta) stacks have beenprepared on epitaxial Ir(111)/Co(111) structures grown on sapphire crystals, in which the spin detector (i.e., top HM) and the spin injector(i.e., Co) are all grown in situ under controlled conditions and present clean and sharp interfaces. We find that a gr monolayer retains the spincurrent injected into the HM from the bottom Co layer. This has been observed by detecting a net reduction in the sum of the spin Seebeckand interfacial contributions due to the presence of gr and independent from the spin Hall angle sign of the HM used.Invited Paper published as part of the special topic on Emerging Materials for Spin-Charge Interconversion

This work shows the possibility of tailoring the magnetic anisotropy direction in ferromagnetic LTP-MnBi thin films from out-of-plane to in-plane while also making possible for the first time the growth of quasi-hexagonal LTP-MnBi micro-islands. This has been managed with no need to apply any external magnetic field, but only by controlling the temperature growth. The rf sputtering of a Mn–Bi composite target produces highly crystalline oriented micro-islands with a size distribution in the micrometer range (up to 80 μm) for samples grown at 300–425 K and oriented elongated threads at 475 K. The oriented films show perpendicular magnetic anisotropy while the oriented ones show in-plane anisotropy. High values of coercivity have been obtained, reaching maximum values of 16.0 and 19.3 kOe at 300 and 400 K, respectively, for these LTP-MnBi thin films. Micromagnetic simulations have shown a clear correlation between the microstructure and the resulting magnetic properties. The route presented here represents a first step towards the possible fabrication of MnBi thin film micromagnets with customized magnetic anisotropy direction based on the deposition temperature.

The development of graphene (Gr) spintronics requires the ability to engineer epitaxial Gr heterostructures with interfaces of high quality, in which the intrinsic properties of Gr are modified through proximity with a ferromagnet to allow for efficient room temperature spin manipulation or the stabilization of new magnetic textures. These heterostructures can be prepared in a controlled way by intercalation through graphene of different metals. Using photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM), we achieve a nanoscale control of thermally activated intercalation of a homogeneous ferromagnetic (FM) layer underneath epitaxial Gr grown onto (111)-oriented heavy metal (HM) buffers deposited, in turn, onto insulating oxide surfaces. XPS and STM demonstrate that Co atoms evaporated on top of Gr arrange in 3D clusters and, upon thermal annealing, penetrate through and diffuse below Gr in a 2D fashion. The complete intercalation of the metal occurs at specific temperatures, depending on the type of metallic buffer. The activation energy and the optimum temperature for the intercalation processes are determined. We describe a reliable method to fabricate and characterize in situ high-quality Gr-FM/HM heterostructures, enabling the realization of novel spin-orbitronic devices that exploit the extraordinary properties of Gr, This research was supported by the Regional Government of Madrid through projects P2018/NMT-4321 (NANOMAGCOST-CM) and P2018/NMT-4511 (NMAT2D) and by the Spanish Ministry of Economy and Competitiveness (MINECO) through projects RTI2018-097895-B-C42, FIS2016-78591-C3-1-R, PGC2018-098613-B-C21, PGC2018-093291-B-I00, FIS2015-67367-C2-1-P, and PCIN-2015-111 (FLAGERA JTC2015 Graphene Flagship “SOgraph”). IFIMAC acknowledges support from the ″Maria de Maeztu″ programme for units of Excellence in R&D (MDM-2014-0377). IMDEA Nanoscience is supported by the “Severo Ochoa” programme for the Centres of Excellence in R&D, MINECO (grant number SEV-2016-0686)

International audience; The crystal structural quality and the strain induced by the substrate strictly impose the magnetic and transport properties of La0.67Sr0.33MnO3 (LSMO) films. In particular, the magnetic anisotropy (MA) of epitaxial LSMO can be finely tuned by varying its thickness and by choosing single crystal substrates with suitable lattice mismatch with the film. Here, we have deposited LSMO films with thicknesses in the 12-50 nm range by pulsed laser deposition on different single crystal substrates inducing either compressive or tensile in-plane strain on the manganites. The epitaxial quality of films was quantified by ω-scans around (002) peak with full-width half-maximum (FWHM) values as low as 0.08° for films on the nearly matched NGO (110) substrate to 1.4° films on high mismatched MgO (001) substrate. As the epitaxial strain in thin-film increases, a significant reduction in metal-insulation transition (MIT) temperature (Tp) was observed. The magnetic properties of the films probed by Kerr magnetometry show that the symmetry of the room temperature MA varies significantly as a function of both strain and thickness. Specifically, we observed pure uniaxial MA on NGO (110) and pure biaxial MA on STO buffered MgO (001), whereas a spin reorientation from uniaxial in-plane to out-of-plane on LSAT (001) and uniaxial to nearly isotropic in-plane on STO (001) substrate as the film thickness is increased. We provide an efficient tool to tune the MA according to the specific spintronic application targeted.

The Valdes Peninsula is a high-value natural area located on the Atlantic coast of the Argentine Patagonia. This research sought to survey raptor species of the peninsula, which has been little investigated. Roadside raptor surveys were carried out along a 451-km roadside transect in November 2012 and in April 2013. Ninety-five diurnal raptors were observed (43 in 2012 and 52 in 2013) comprising a total of 9 species. The most detected species were Cathartes aura and Milvago chimango. The abundances recorded in our study were lower than those obtained in other similar studies in continental Patagonia.

A major challenge for future spintronics is to develop suitable spin transport channels with long spin lifetime and propagation length. Graphene can meet these requirements, even at room temperature. On the other side, taking advantage of the fast motion of chiral textures, i.e., N\'eel-type domain walls and magnetic skyrmions, can satisfy the demands for high-density data storage, low power consumption and high processing speed. We have engineered epitaxial structures where an epitaxial ferromagnetic Co layer is sandwiched between an epitaxial Pt(111) buffer grown in turn onto MgO(111) substrates and a graphene layer. We provide evidence of a graphene-induced enhancement of the perpendicular magnetic anisotropy up to 4 nm thick Co films, and of the existence of chiral left-handed N\'eel-type domain walls stabilized by the effective Dzyaloshinskii-Moriya interaction (DMI) in the stack. The experiments show evidence of a sizeable DMI at the gr/Co interface, which is described in terms of a conduction electron mediated Rashba-DMI mechanism and points opposite to the Spin Orbit Coupling-induced DMI at the Co/Pt interface. In addition, the presence of graphene results in: i) a surfactant action for the Co growth, producing an intercalated, flat, highly perfect fcc film, pseudomorphic with Pt and ii) an efficient protection from oxidation. The magnetic chiral texture is stable at room temperature and grown on insulating substrate. Our findings open new routes to control chiral spin structures using interfacial engineering in graphene-based systems for future spin-orbitronics devices fully integrated on oxide substrates., Comment: 10 pages, 6 figures

Inelastic helium atom scattering (HAS) is suitable to determine low-energy (few meV) vibrations spatially localized on structures in the nanometer range. This is illustrated for the nanodomes that appear often on graphene (Gr) epitaxially grown on single crystal metal surfaces. The nature of the inelastic losses observed in Gr/Ru(0001) and Gr/Cu/Ru(0001) has been clarified by intercalation of Cu below the Gr monolayer, which decouples the Gr layer from the Ru substrate and changes substantially the out-of-plane, flexural phonon dispersion of epitaxial Gr, while maintaining the nanodomes and their localized vibrations. He diffraction proves that the Cu-intercalated Gr layer is well ordered structurally, while scanning tunneling microscopy reveals the persistence of the (slightly modified) periodic array of Gr nanodomes. A simple model explains the order of magnitude of the energy losses associated with the Gr nanodomes and their size dependence. The dispersionless, low-energy phonon branches may radically alter the transport of heat in intercalated Gr.

Diversity metrics are commonly used to measure or quantify species-level biodiversity in a given area. In recent decades, ecologists developed many measures and indices in order to quantify a larger proportion of information about communities or species assemblages. Commonly these measures are based on species richness or species evenness, in relation to their relative abundance. Among the most common diversity metrics are the indices of taxonomic diversity, functional diversity and phylogenetic diversity. These metrics are often used to assess effectiveness of conservation planning. One concern on the use of many diversity metrics, especially in modeling, is the potential redundancy among these indices and measures. Many scientists explored the associations among different diversity metrics, finding clear patterns. For instance, functional richness and the functional diversity (FD) index are both positively correlated with species richness, while functional evenness should be unrelated to species richness. Furthermore, explorations focusing on associations between phylogenetic diversity and taxonomic or functional diversity metrics are few. However, despite the importance of the types of environment has on biotic assemblage rules, there are no studies comparing the association among diversity metrics across different type of environments. Here, we found higher values of taxonomic diversity, functional richness and Rao’s quadratic entropy (RaoQ) in farmland than in forests and grasslands. Forest bird communities were characterized by a large amount of evolutionary history as reflected by community evolutionary distinctiveness (CED). Furthermore, associations among diversity and community metrics in bird communities differ across types of environments. Within functional diversity metrics, associations between functional richness and RaoQ as well as associations between functional evenness and divergence were always positive, independently of the type of environment. The associations between functional richness and evenness or divergence, as well as functional evenness and RaoQ, changed strength and direction of correlation between different types of environment. In conclusion, a) large scale conservation planning strategies have to consider that different environments support different dimensions of bird diversity, and b) when modeling many diversity metrics, associations among diversity and community metrics can also change across environments.

We have studied a series of Pt/Co/M epitaxial trilayers, in which Co is sandwiched between Pt and a non magnetic layer M (Pt, Ir, Cu, Al). Using polar magneto-optical Kerr microscopy, we show that the field- induced domain wall speeds are strongly dependent on the nature of the top layer, they increase going from M=Pt to lighter top metallic overlayers, and can reach several 100 m/s for Pt/Co/Al. The DW dynamics is consistent with the presence of chiral N\'eel walls stabilized by interfacial Dzyaloshinskii-Moriya interaction (DMI) whose strength increases going from Pt to Al top layers. This is explained by the presence of DMI with opposite sign at the Pt/Co and Co/M interfaces, the latter increasing in strength going towards heavier atoms, possibly due to the increasing spin-orbit interaction. This work shows that in non-centrosymmetric trilayers the domain wall dynamics can be finely tuned by engineering the DMI strength, in view of efficient devices for logic and spitronics applications., Comment: 5 pages, 4 Figures

Species distribution models are often used to study the biodiversity of ecosystems. The modelling process uses a number of parameters to predict others, such as the occurrence of determinate species, population size, habitat suitability or biodiversity. It is well known that the heterogeneity of landscapes can lead to changes in species’ abundance and biodiversity. However, landscape metrics depend on maps and spatial scales when it comes to undertaking a GIS analysis. We explored the goodness of fit of several models using the metrics of landscape heterogeneity and altitude as predictors of bird diversity in different landscapes and spatial scales. Two variables were used to describe biodiversity: bird richness and trophic level diversity, both of which were obtained from a breeding bird survey by means of point counts. The relationships between biodiversity and landscape metrics were compared using multiple linear regressions. All of the analyses were repeated for 14 different spatial scales and for cultivated, forest and grassland environments to determine the optimal spatial scale for each landscape typology. Our results revealed that the relationships between species’ richness and landscape heterogeneity using 1:10,000 land cover maps were strongest when working on a spatial scale up to a radius of 125–250 m around the sampled point (circa 4.9–19.6 ha). Furthermore, the correlation between measures of landscape heterogeneity and bird diversity was greater in grasslands than in cultivated or forested areas. The multi-spatial scale approach is useful for (a) assessing the accuracy of surrogates of bird diversity in different landscapes and (b) optimizing spatial model procedures for biodiversity mapping, mainly over extensive areas.

We demonstrate that the interfacial exchange coupling in ferromagnetic/antiferromagnetic (FM/AFM) systems induces symmetry breaking of the spin-orbit (SO) effects. This has been done by studying the field and angle dependencies of anisotropic magnetoresistance and vectorial-resolved magnetization hysteresis loops, measured simultaneously and reproduced with numerical simulations. We show how the induced unidirectional magnetic anisotropy at the FM/AFM interface results in strong asymmetric transport behaviors, which are chiral around the magnetization hard-axis direction. Similar asymmetric features are anticipated in other SO-driven phenomena, This work was supported in part by the Spanish MINECO through Projects No. MAT2012-39308, No. FIS2013-40667-P, No. MAT2011-25598, and No. MAT2014-52477-C5-3-P, and by the Comunidad de Madrid through Project No. S2013/MIT-2850 (NANOFRONTMAG-CM). P.P. and A.B. acknowledge support through the Marie Curie AMAROUT EU Programme, and through MINECO “Juan de la Cierva” (JCI-2011-09602) and “Ramón y Cajal” contracts

Spin-Orbit (SO) effects of a ferromagnetic (FM) layer can be artificially modified by interfacial exchange coupling with an anti-ferro magnet (AFM). Non-symmetric magnetization reversals as well as asymmetric transport behaviors are distinctive signatures of the symmetry-breaking induced by such interfacial coupling. We present a complete picture of the symmetry of the SO effects by studying the magneto-transport properties of single FM film and FM/AFM systems (exchanged-biased bilayer and spin-valve structures) with specific in-plane magnetic anisotropy. Single FM films with a well-defined (two-fold) uniaxial magnetic anisotropy display symmetric magnetization reversals and magneto-resistance responses for any value and direction of the applied magnetic field. On the contrary, in the exchange-biased structures, the exchange interaction at the interface between the FM and AFM layers is responsible of chiral asymmetries in magnetization reversal pathways as well as in the magneto-resistance behaviors. Such asymmetries are directly related to the additional unidirectional (one-fold) magnetic anisotropy imposed by the AFM. In particular, chiral reversals and MR responses are found around the magnetization hard-axis direction. This has been shown in FM/AFM bilayer and spin-valve (where the MR outputs are related to different transport phenomena, i.e. anisotropic magneto-resistance and giant magneto-resistance respectively), hence indicating that the chiral asymmetries are intrinsic of systems with unidirectional anisotropy.

The Stoner-Wohlfarth (SW) model is the simplest model that describes adequately the magnetization reversal of nanoscale systems that are small enough to contain single magnetic domains. However for larger sizes where multi-domain effects are present, e.g., in thin films, this simple macrospin approximation fails and the experimental critical curve, referred as SW astroid, is far from its predictions. Here we show that this discrepancy could vanish also in extended system. We present a detailed angular-dependent study of magnetization reversal dynamics of a thin film with well-defined uniaxial magnetic anisotropy, performed over 9 decades of applied field sweep rate (dH/dt). The angular-dependent properties display a gradual transition from domain wall pinning and motion-like behaviour to a nucleative single-particle one, as dH/dt increases. Remarkably, in the high dynamic regime, where nucleation of reversed domains is the dominant mechanism of the magnetization reversal (nucleative regime), the magnetic properties including the astroid become closer to the ones predicted by SW model. The results also show why the SW model can successfully describe other extended systems that present nucleative regime, even in quasi-static conditions, This work has been supported by MINECO (Ministerio de Economía y Competitividad) through Projects No. MAT2012-39308, FIS2015-67287-P, and FIS2016-78591-C3-1-R, by the Comunidad de Madrid through Project S2013/MIT-2850 NANOFRONTMAG-CM, and by MINECO through the FLAGERA Programme of Graphene Flagship: SOgraph project (No. PCIN-2015-216); and M-era.Net Programme: NEXMAG project (PCIN- 2015-126). IMDEA-Nanociencia acknowledges support from the ‘Severo Ochoa’ Program for Centres of Excellence in R&D (MINECO, Grant SEV-2016-0686). P.P. acknowledges support through the Marie Curie AMAROUT EU Programme and JCI-2011-09602. A.B. acknowledges MINECO through the ENMA-National project (MAT2014-56955-R).

The magnetoresistance (MR) effect is widely employed in technologies that pervade our world from magnetic reading heads to sensors. Diverse contributions to MR, such as anisotropic, giant, tunnel, colossal, and spin-Hall, are revealed in materials depending on the specific system and measuring configuration. Half-metallic manganites hold promise for spintronic applications but the complexity of competing interactions has not permitted the understanding and control of their magnetotransport properties to enable the realization of their technological potential. Here we report on the ability to induce a dominant switchable magnetoresistance in La0.7Sr0.3MnO3 epitaxial films, at room temperature (RT). By engineering an extrinsic magnetic anisotropy, we show a large enhancement of anisotropic magnetoresistance (AMR) which leads to, at RT, signal changes much larger than the other contributions such as the colossal magnetoresistance (CMR). The dominant extrinsic AMR exhibits large variation in the resistance in low field region, showing high sensitivity to applied low magnetic fields. These findings have a strong impact on the real applications of manganite based devices for the high-resolution low field magnetic sensors or spintronics., Comment: 10 pages, 6 figures

International audience; We investigate the in-plane magnetic anisotropy in La 0.67 Sr 0.33 MnO 3 thin films grown on SrTiO 3 (001) substrate using angular dependent room temperature Vectorial Magneto-Optical Kerr Magnetometry. The experimental data reveals that the magnetic anisotropy symmetry landscape significantly changes depending upon the strain and thickness. At low film thickness (12 and 25 nm) the dominant uniaxial anisotropy is due to interface effects, step edges due to mis-cut angle of SrTiO 3 substrate. At intermediate thickness, the magnetic anisotropy presents a competition between magnetocrystalline (biaxial) and substrate step induced (uniaxial) anisotropy. Depending upon their relative strengths, a profound biaxial or uniaxial or mixed anisotropy is favoured. Above the critical thickness, magnetocrystalline anisotropy dominates all other effects and shows a biaxial anisotropy.

We measured high resolution Cu $L_3$ edge resonant inelastic x-ray scattering (RIXS) of the undoped cuprates La$_2$CuO$_4$, Sr$_2$CuO$_2$Cl$_2$, CaCuO$_2$ and NdBa$_2$Cu$_3$O$_6$. The dominant spectral features were assigned to $dd$ excitations and we extensively studied their polarization and scattering geometry dependence. In a pure ionic picture, we calculated the theoretical cross sections for those excitations and used them to fit the experimental data with excellent agreement. By doing so, we were able to determine the energy and symmetry of Cu-3$d$ states for the four systems with unprecedented accuracy and confidence. The values of the effective parameters could be obtained for the single ion crystal field model but not for a simple two-dimensional cluster model. The firm experimental assessment of $dd$ excitation energies carries important consequences for the physics of high $T_c$ superconductors. On one hand, having found that the minimum energy of orbital excitation is always $\geq 1.4$ eV, i.e., well above the mid-infrared spectral range, leaves to magnetic excitations (up to 300 meV) a major role in Cooper pairing in cuprates. On the other hand, it has become possible to study quantitatively the effective influence of $dd$ excitations on the superconducting gap in cuprates., 22 pages, 11 figures, 1 table

We investigate the symmetry-breaking effects of magnetic nanostructures that present unidirectional (one-fold) magnetic anisotropy. Angular and field dependent transport and magnetic properties have been studied in two different exchange-biased systems, i.e. ferromagnetic (FM)/ antiferromagnetic (AFM) bilayer and spin-valve structures. We experimentally show the direct relationships between the magnetoresistance (MR) response and the magnetization reversal pathways for any field value and direction. We demonstrate that even though the MR signals are related to different transport phenomena, namely anisotropic magnetoresistance (AMR) and giant magnetoresistance (GMR), chiral asymmetries are found around the magnetization hard-axis direction, in both cases originated from the one-fold symmetry of the interfacial exchange coupling. Our results indicate that the chiral asymmetry of transport and magnetic behaviors are intrinsic of systems with an unidirectional contribution, This work was supported in part by the Spanish MINECO through Project No. MAT2012-39308, FIS2013-40667-P and MAT2014-52477-C5-3-P, and by the Comunidad de Madrid through Project S2013/MIT-2850 (NANOFRONTMAG-CM). P.P. acknowledges support through Marie Curie AMAROUT EU Programme and JCI-2011-09602.

We investigated the role of strain on the magnetic properties of La0.7Sr0.3MnO3 epitaxial films grown on substrates with different crystallographic orientation. The magnetic characterization confirms the large magnetostriction due to the tensile stress applied by the SrTiO3 substrates. The data demonstrate that the easy direction of magnetization is aligned to the elongated, in-plane axis both in (110)- and (001)-oriented films. The in-plane anisotropy of (110) films is interpreted in the frame of a simple structural model. We provide evidence of a spatial separation between a conducting ferromagnetic and an insulating paramagnetic phase at the Curie temperature. The possible effect of such phase separation on the coercitive field and on the magnetization versus temperature is discussed. (c) 2006 Elsevier B.V. All rights reserved.

The discovery that the interface between two band gap insulators LaAlO3 and SrTiO3 is highly conducting has raised an enormous interest in the field of oxide electronics. The LAlO3/SrTiO3 interface can be tuned using an electric field and switched from a superconducting to an insulating state. Conducting paths in an insulating background can be written applying a voltage with the tip of an atomic force microscope, creating great promise for the development of a new generation of nanoscale electronic devices. However, the mechanism for interface conductivity in LaAlO3/SrTiO3 has remained elusive. The theoretical explanation based on an intrinsic charge transfer (electronic reconstruction) has been strongly challenged by alternative descriptions based on point defects. In this work, thanks to modern aberration-corrected electron probes with atomic-scale spatial resolution, interfacial charge and atomic displacements originating the electric field within the system can be simultaneously measured, yielding unprecedented experimental evidence in favor of an intrinsic electronic reconstruction., Accepted for publication in Advanced Materials. Published online on 06/20/2012

The development of smart, nano-scale, low-power-consumption spintronic-based devices has been made possible through recent advances in modern fabrication and characterization nanomagnetism technologies. Dimensionality and interfacial effects promote much of the new properties observed in complex multi-layered nanostructures. The development of polarization-dependent X-ray based techniques has contributed essentially to our present level of fundamental understanding of artificial nanostructures that exhibit unexpected collective phenomena. In this contribution, some of the recent developments in spintronic as well as in advanced synchrotron-based instrumentation will be reviewed. Future trends focused on both experimental improvements and new scientific issues are discussed.

Here, we report on a versatile full angular resolved/broad temperature range/vectorial magneto optical Kerr effect (MOKE) magnetometer, named TRISTAN. Its versatility relies on its capacity to probe temperature and angular dependencies of magnetization reversal processes without the need to do any intervention on the apparatus during measurements. The setup is a combination of a vectorial MOKE bench and a cryostat with optical access. The cryostat has a motorized rotatable sample holder with azimuthal correction. It allows for simultaneous and quantitative acquisition of the two in-plane magnetization components during the hysteresis loop at different temperatures from 4 K up to 500 K and in the whole angular range, without neither changing magnet orientation nor opening the cryostat. Measurements performed in a model system with competing collinear biaxial and uniaxial contributions are presented to illustrate its capabilities, P.P. acknowledges financial support from MINECO through Contract No. JCI-2011- 09602. F.J.T. acknowledges financial support from Ramon y Cajal program (RYC-2011-09617). This work has been supported by MINECO through Project Nos. MAT2011-25598 and MAT2012-39308, by the Comunidad de Madrid through Project No. S2013/MIT-2850 NANOFRONTMAG-CM and by EU-FP7 through NANOPYME Project (No. 310516)

Angle- and temperature-dependent vectorial magnetometry measurements are necessary to disentangle the effective magnetic symmetry in magnetic nanostructures. Here we present a detailed study on an Fe(1 0 0) thin film system with competing collinear biaxial (four-fold symmetry) and uniaxial (two-fold) magnetic anisotropies, carried out with our recently developed full angular/broad temperature range/vectorial-resolved magneto-optical Kerr effect magnetometer, named TRISTAN. The data give direct views on the angular and temperature dependence of the magnetization reversal pathways, from which characteristic axes, remanences, critical fields, domain wall types, and effective magnetic symmetry are obtained. In particular, although the remanence shows four-fold angular symmetry for all investigated temperatures (15 K-400 K), the critical fields show strong temperature and angular dependencies and the reversal mechanism changes for specific angles at a given (angle-dependent) critical temperature, showing signatures of an additional collinear two-fold symmetry. This symmetry-breaking is more relevant as temperature increases to room temperature. It originates from the competition between two anisotropy contributions with different symmetry and temperature evolution. The results highlight the importance of combining temperature and angular studies, and the need to look at different magnetic parameters to unravel the underlying magnetic symmetries and temperature evolutions of the symmetry-breaking effects in magnetic nanostructures.

We present novel low-field magnetoresistive devices based on the ferromagnetic manganite La0.7Sr0.3MnO3 operating in the current in plane (CIP) configuration. In these planar spin-valve devices, a focused Ga+ beam is used to create pinning centers for magnetic domain walls. The spin-dependent scattering of polarized electrons at the domain walls (DW) is responsible for the magnetoresistance observed in the patterned tracks. The magneto-transport properties of these devices are interpreted within a model for DW magnetoresistance. Applications such as magnetic data storage can be envisaged for the structures we investigated. (C) 2006 Elsevier B.V. All rights reserved.

We present an experimental study devoted to determine the magnetoresistive signals as imposed by the system magnetic anisotropy and applied current direction in a model ferromagnetic system. By having direct experimental access to the magnetization vector during the reversal (measured through angular- and field-dependent vectorial-resolved magnetization loops), we can predict both longitudinal and transverse magnetoresistive signals, i.e., anisotropic magnetoresistance and planar Hall effect. This has been done by experimentally disclosing the resistance changes occurring during (and simultaneously to) the magnetization reversal processes. © 2014 AIP Publishing LLC., This work was supported in part by the Spanish MINECO through Projects Nos. MAT2012-39308 and MAT2011-25598 and Comunidad de Madrid through the Project No. S2009/MAT-1726. P.P. acknowledges support through the JCI-2011-09602 Contract from the Spanish MINECO and through the Marie Curie AMAROUT EU Programme.

A vectorial magneto-optic Kerr effect (v-MOKE) setup with simultaneous and quantitative determination of the two in-plane magnetization components is described. The setup provides both polarization rotations and reflectivity changes at the same time for a given sample orientation with respect to a variable external magnetic field, as well as allowing full angular studies. A classical description based on the Jones formalism is used to calculate the setup's properties. The use of different incoming light polarizations and/or MOKE geometries, as well as the errors due to misalignment and solutions are discussed. To illustrate the capabilities of the setup a detailed study of a model four-fold anisotropy system is presented. Among others, the setup allows to study the angular dependence of the hysteresis phenomena, remanences, critical fields, and magnetization reversal processes, as well as the accurate determination of the easy and hard magnetization directions, domain wall orientations, and magnetic anisotropies.

A site-dependent charge transfer to 7,7′,8,8′-tetracyanoquinodimethane (TCNQ) adsorbed on a single layer of periodically rippled graphene grown epitaxially on Ru(0001), identified by X-ray photoemission techniques, can be spatially resolved using Scanning Tunneling Microscopy, which can also detect the formation of magnetic moments. The molecules adsorbed on the lower part of the ripples are charged with electrons donated from the doped graphene overlayer and develop a magnetic moment, while those at the upper part of the ripples are neutral. On the other hand, TCNQ adsorbed on graphene on Ir(111) shows negligible charge transfer and no magnetic moment. These observations explain the spatially dependent long-range magnetic order observed recently for TCNQ on gr/Ru(0001).

Perna, P. et al., The simultaneous determination of magnetoresistance and vectorial-resolved magnetization hysteresis curves in a spin valve structure reveals distinct magnetoresistive features for different magnetic field orientations, which are directly related to the magnetization reversal processes. Measurements performed in the whole angular range demonstrate that the magnetoresistive response originates from the intrinsic anisotropic angular dependence of the magnetization orientation between the two ferromagnetic layers. This also provides direct proof that the spin-dependent scattering in the bulk of the magnetic layers is at the origin of the magnetoresistive signal. © 2012 American Physical Society., This work was supported in part by the Spanish MICINN through Project No. CSD2007-00010 and FIS 2010-18847 and by the Comunidad de Madrid through Project No. S2009/MAT-1726. P.P. acknowledges support through the Marie Curie AMAROUT EU action and the Spanish MICINN “Juan de la Cierva” contract. A.B. acknowledges support through the “Ramón y Cajal” contract from the Spanish MICINN.

International audience; We have observed the in-plane magnetic domain arrangement during magnetization reversal in a 40 nm thick La0.7Sr0.3MnO3/SrTiO3 (001) thin film patterned into 500 lm long microbridges of width 50 or 100 lm. Magneto-optical Kerr effect microscopy was used at room temperature and magnetic hysteresis loops were deduced from local averaging of intensity over the microbridge areas. Magnetization reversal proceeds by nucleation and propagation of 180 domain walls. When the magnetic field was applied parallel to the bridge, we observed the nucleation of only one or two domain walls and the reversal occurred by the propagation of them. When the magnetic field was applied perpendicular to the bridge, the reversal occurred mostly by the nucleation of several domain walls. The low field magnetoresistance (MR) and the low frequency noise at zero magnetic field were measured at room temperature. In addition to the linear and reversible colossal MR effect, hysteretic MR versus magnetic field curves could be observed, showing two maxima (minima) when the magnetic field is parallel (perpendicular) to the bridge length. The observed hysteretic MR behaviour is attributed to anisotropic MR inside the 180 Ne'el domain walls.

We show a detailed magneto-optical Kerr study at room temperature of well characterized epitaxial La0.7Sr0.3MnO3 (LSMO) thin films grown onto (110) and (118) SrTiO3 substrates. The films present a well-defined uniaxial (two-fold) magnetic anisotropy ascribed to substrate-induced anisotropy. In particular, the in-plane uniaxial anisotropy in the(110)-oriented LSMO films originates from the existence of elongated in-plane [001]-oriented structures. Similar elongated structures, parallel to the [110] crystallographic direction, are found for LSMO films grown on (118) STO surfaces. In all films, such a uniaxial magnetic anisotropy is characterized by an easy axis lying along the elongated structures. Furthermore, the vectorial-resolved hysteresis loops as a function of the in-plane applied field direction are interpreted in terms of rotation and propagation and nucleation of magnetic domains processes. Our results demonstrate the tailoring of magnetic anisotropy by exploiting the substrate-induced anisotropy in epitaxial thin films, This work was supported in part by the Spanish MICINN through Project No. CSD2007-00010 and by the Comunidad de Madrid through Project No. S2009/MAT-1726. P.P. thanks the European Science Foundation (ESF) through the activity entitled ’Thin Films for Novel Oxide Devices’ (http://www.ims.tnw.utwente.nl/thiox/) for partial financial support through exchange grants

The following article appeared in Journal of Applied Physics 110.1 (2011): 013919 and may be found at http://scitation.aip.org/content/aip/journal/jap/110/1/10.1063/1.3605542, We present a detailed study on the magnetic properties, including anisotropy, reversal fields, and magnetization reversal processes, of well characterized half-metallic epitaxial La0.7Sr0.3MnO 3 (LSMO) thin films grown onto SrTiO3 (STO) substrates with three different surface orientations, i.e., (001), (110), and (1 1̄8). The latter shows step edges oriented parallel to the [110] (in-plane) crystallographic direction. Room temperature high resolution vectorial Kerr magnetometry measurements have been performed at different applied magnetic field directions in the whole angular range. In general, the magnetic properties of the LSMO films can be interpreted with just the uniaxial term, with the anisotropy axis given by the film morphology, whereas the strength of this anisotropy depends on both structure and film thickness. In particular, LSMO films grown on nominally flat (110)-oriented STO substrates presents a well defined uniaxial anisotropy originated from the existence of elongated in-plane [001]-oriented structures, whereas LSMO films grown on nominally flat (001)-oriented STO substrates show a weak uniaxial magnetic anisotropy, with the easy axis direction aligned parallel to residual substrate step edges. Elongated structures are also found for LSMO films grown on vicinal STO(001) substrates. These films present a well-defined uniaxial magnetic anisotropy, with the easy axis lying along the step edges, and its strength increases with the LSMO thickness. It is remarkable that this step-induced uniaxial anisotropy has been found for LSMO films up to 120 nm thickness. Our results are promising for engineering novel half-metallic magnetic devices that exploit tailored magnetic anisotropy., This work was supported in part by the Spanish MICINN through Project Nos. CSD2007-00010 and MAT2010-21822 and by the Comunidad de Madrid through Project No. S2009/MAT-1726. P.P. acknowledges support through the Marie Curie AMAROUT EU programme and thanks the European Science Foundation (ESF) through the activity entitled ‘Thin Films for Novel Oxide Devices’ (http://www.ims.tnw.utwente. nl/thiox/) for partial financial support through exchange grants. The authors wish to thank Ch. Simon at CRISMAT (UMR6508) for SQUID magnetization measurements and CRISMAT laboratory (UMR6508) at ENSICAEN for the LSMO target fabrication. The authors are also very grateful to U. Scotti di Uccio at CNR-SPIN Naples for fruitful discussions and for the use of the x ray diffractometer.