A5004169197- Magnetic and transport properties of perovskites and related materials
- Magnetic properties of thin films
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Magnetic Properties of Alloys
- Multiferroics and related materials
- Quantum and electron transport phenomena
- Electronic and Structural Properties of Oxides
- Shape Memory Alloy Transformations
- Magnetic Properties and Applications
- Physics of Superconductivity and Magnetism
- Magneto-Optical Properties and Applications
- Magnetic Properties and Synthesis of Ferrites
- Theoretical and Computational Physics
- Thermal Expansion and Ionic Conductivity
- Surface and Thin Film Phenomena
- Iron-based superconductors research
- High-pressure geophysics and materials
- Metallic Glasses and Amorphous Alloys
- Iron oxide chemistry and applications
- ZnO doping and properties
- Topological Materials and Phenomena
- Ferroelectric and Piezoelectric Materials
- Superconductivity in MgB2 and Alloys
- Metallurgical and Alloy Processes
Universidad de Zaragoza
2014-2024
Instituto de Nanociencia y Materiales de Aragón
2012-2024
Consejo Superior de Investigaciones Científicas
2003-2021
Advanced Institute of Materials Science
2016
Tohoku University
2016
Universidade do Porto
2016
Japan Science and Technology Agency
2016
Fundacion Agencia Aragonesa para la Investigacion y el Desarrollo
2013
Universitas Islam Al-Azhar Mataram
2003
Institut Laue-Langevin
2002
We present direct evidence that the giant magnetocaloric effect recently discovered in ${\mathrm{Gd}}_{5}{(\mathrm{S}\mathrm{i}}_{1.8}{\mathrm{Ge}}_{2.2})$ alloy is associated with a field-induced first-order structural transition from ${P112}_{1}/a$ monoclinic (paramagnetic) to Pnma orthorhombic (ferromagnetic) structure. A large volume contraction of $\ensuremath{\Delta}V/V\ensuremath{\cong}0.4%$ takes place spontaneously at temperature, ${T}_{C}\ensuremath{\cong}240\mathrm{K}.$ The...
We present tunneling experiments on Fe(001)/MgO(20 Å)/FeCo(001) single-crystal epitaxial junctions of high quality grown by sputtering and laser ablation. Tunnel magnetoresistance measurements give 60% at 30 K, to be compared with 13% obtained recently (001)-oriented Fe/amorphous-Al2O3/FeCo tunnel junctions. This difference demonstrates that the spin polarization electrons is not directly related density states free metal surface—Fe(001) in this case—but depends actual electronic structure...
Room temperature x-ray diffraction, magnetization and neutron diffraction measurements up to 500 K have been carried out on polycrystalline bulk double perovskites AA'FeMoO6 (AA' = Ba2, BaSr, Sr2, Ca2) in order determine correlate their structural magnetic properties. As the average ionic radius is diminished, crystallographic structure evolves from cubic (for AA' BaSr) tetragonal (Sr2) finally monoclinic (Ca2). In case of a novel crossover high paramagnetic state low ferrimagnetic has...
We report that the first-order antiferromagnetic to ferromagnetic transition in Ge-rich magnetocaloric compound ${\mathrm{Gd}}_{5}{(\mathrm{S}\mathrm{i}}_{0.1}{\mathrm{Ge}}_{0.9}{)}_{4}$ is associated with a structural phase transformation from high-temperature ${\mathrm{Gd}}_{5}{\mathrm{Ge}}_{4}$-type Pnma low-temperature ${\mathrm{Gd}}_{5}{\mathrm{Si}}_{4}$-type orthorhombic structure. This magnetostructural can be triggered reversibly by application of an external magnetic field,...
The onset of a Griffiths-like phase has been observed in Tb5Si2Ge2 (TC=110 K) by means magnetic susceptibility and small-angle neutron scattering experiments. We show the growth ferromagnetic cluster system characterized an inverse exponent lower than unity at TC<T<TG approximately 200 K. suggest that state is originated local disorder within crystallographic structure, stabilized enhanced competing intralayer interlayer interactions. Both factors thus promote segregation nanometric regions with
We report the first experimental observation of spin Seebeck effect in magnetite thin films. The signal observed at temperatures above Verwey transition is a contribution from both anomalous Nernst (ANE) and effects (SSE). ANE Fe3O4 layer to SSE found be negligible due resistivity difference between Pt layers. Below free ferromagnetic it also dominate over magnetic proximity on layer.
We report a complete characterization of the anomalous Nernst effect (ANE) and its relationship with Hall (AHE) in ${\mathrm{Fe}}_{3}{\mathrm{O}}_{4}$. By combining full thermoelectric electric transport measurements as function temperature, we have verified that universal scaling relation between diagonal conductivities (${\ensuremath{\sigma}}_{zy}\ensuremath{\propto}{\ensuremath{\sigma}}_{zz}^{1.6}$), observed materials bad-metal-hopping type conduction, is also applicable to transport....
Spin-orbitronics, which exploits the coupling between spin and orbital momentum of electrons, relies on possibility to electrically create detect pure currents without need ferromagnetic elements. An efficient way achieve this spin-to-charge conversion (and vice versa) is expected by exploiting Rashba-Edelstein effect. This phenomenon related well-known Hall effect, but in former, current occurs at interface materials with a strong splitting surface states, instead bulk. paper reports an...
Zero-field electrical resistivity over the temperature range of 4–300 K and magnetoresistance in magnetic fields up to 12 T have been measured Gd5(Si1.8Ge2.2). This system undergoes a first-order magnetostructural transition at TC≅240 K, from high-temperature paramagnetic low-temperature ferromagnetic phase, accompanied by large drop resistivity. The application an external field above TC can induce this transition, giant negative effect (Δρ/ρ≅−20%) is observed associated with field-induced...
Effects of temperature and pressure on magnetic, elastic, structural, thermal properties Tb5Si2Ge2 have been studied by means macroscopic (thermal expansion magnetization) microscopic (neutron powder diffraction) techniques. We present evidence that the high-temperature second-order ferromagnetic transition can be coupled with low-temperature first-order structural phase change into a single magnetic-crystallographic transformation at above tricritical point in vicinity 8.6 kbar. This...
Thermal spin pumping constitutes a novel mechanism for generation of currents; however their weak intensity major roadblock its usefulness. We report phenomenon that produces huge current in the central region multilayer system, resulting giant Seebeck effect structure formed by repetition ferromagnet/metal bilayers. The result is consequence interconversion magnon and electron currents at multiple interfaces. This work opens possibility to design thin film heterostructures may boost...
Terahertz emission spectroscopy of ultrathin multilayers magnetic and heavy metals has recently attracted much interest. This method not only provides fundamental insights into photoinduced spin transport spin-orbit interaction at highest frequencies but also paved the way to applications such as efficient ultrabroadband emitters terahertz electromagnetic radiation. So far, predominantly standard ferromagnetic materials have been exploited. Here, by introducing a suitable figure merit, we...
We show here that using spin orbit coupling interactions at a metallic interface it is possible to control the sign of charge conversion in pumping experiment. Using intrinsic symmetry “Inverse Rashba Edelstein Effect” (IREE) Bi/Ag interface, current changes when reversing order Ag and Bi stacking. This confirms IREE nature into these interfaces opens way tailoring sensing voltage by an appropriate trilayer sequence.
We present direct evidence of the phase segregation and magnetic-field-induced structural transition in ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}$ as proposed earlier [R. Mahendiran et al., Phys. Rev. Lett. 82, 2191 (1999)] for collapse charge-ordered insulating state. The spontaneous $(H=0)$ low-temperature at 125 K is found to be segregated into two different crystallographic structures three magnetic phases: orthorhombic (Imma) ferromagnetic, A-type antiferromagnetic,...
The giant magnetocaloric compound Gd5Ge4 is the only member of Gd5(SixGe1-x)4 family where three-dimensional exchange interactions between two-dimensional correlated layers crystallographic structure are so weak that spontaneous ferromagnetism does not set in at any temperature. In this Letter we explore possibility to reach ferromagnetic state by application hydrostatic pressure. Linear thermal expansion and magnetic measurements under pressure reveal reduction unit cell volume induces a...
The composition dependence of magnetic and structural transformations, as well the temperature magnetocrystalline anisotropy, were studied in martensitic Ni2+xMn1+yGa1+z (x+y+z=0) Heusler alloys. Moving away from stoichiometric composition, a slight variation, large reduction, marked enhancement, were, respectively, observed for Curie temperature, (martensitic–austenitic) transformation temperatures.
We study the influence of cation size in magnetic properties ${(AA}^{\ensuremath{'}}{)}_{2}{\mathrm{FeReO}}_{6}$ ${(AA}^{\ensuremath{'}}={\mathrm{Ba}}_{2},{\mathrm{Ba}}_{1.5}{\mathrm{Sr}}_{0.5},{\mathrm{B}\mathrm{a}\mathrm{S}\mathrm{r},\mathrm{B}\mathrm{a}}_{0.5}{\mathrm{Sr}}_{1.5},{\mathrm{Sr}}_{2},{\mathrm{Ca}}_{0.5}{\mathrm{Sr}}_{1.5},{\mathrm{C}\mathrm{a}\mathrm{S}\mathrm{r},\mathrm{C}\mathrm{a}}_{1.5}{\mathrm{Sr}}_{0.5},{\mathrm{Ca}}_{2})$ double perovskites. As average decreases,...
We report Hall-effect measurements of epitaxial Fe (001) thin films grown on MgO (001). have focused the dependence anomalous Hall effect (AHE) in heteroepitaxial structures $\text{MgO}\text{ }(001)//\text{Fe}(t)/\text{MgO}$ with $t=10$, 2.5, 2, 1.8, and 1.3 nm. Our results been interpreted terms a recent unified theory AHE. demonstrated that thickness roughness layer are control parameters to tune both longitudinal conductivity ${\ensuremath{\sigma}}_{xx}$ ${\ensuremath{\sigma}}_{xy}$. In...
We study the enhanced magnetic moment observed in epitaxial magnetite $({\text{Fe}}_{3}{\text{O}}_{4})$ ultrathin films $(t<15\text{ }\text{nm})$ grown on MgO (001) substrates by means of pulsed laser deposition. The ${\text{Fe}}_{3}{\text{O}}_{4}$ thin exhibit high crystallinity, low roughness, and sharp interfaces with substrate, existence Verwey transition at thicknesses down to 4 nm. evolution temperature film thickness shows a dependence antiphase boundaries density. Superconducting...
Epitaxial films of ${\mathrm{SrMnO}}_{3}$ and bilayers ${\mathrm{SrMnO}}_{3}/{\mathrm{La}}_{0.67}{\mathrm{Sr}}_{0.33}{\mathrm{MnO}}_{3}$ have been deposited by pulsed laser deposition on different substrates, namely, ${\mathrm{LaAlO}}_{3}$ (001), $({\mathrm{LaAlO}}_{3}{)}_{0.3}({\mathrm{Sr}}_{2}{\mathrm{AlTaO}}_{6}{)}_{0.7}$ ${\mathrm{SrTiO}}_{3}$ allowing us to perform an exhaustive study the dependence antiferromagnetic order exchange bias field epitaxial strain. The N\'eel temperatures...
Spin transport is crucial for future spintronic devices operating at bandwidths up to the terahertz (THz) range. In F|N thin-film stacks made of a ferro/ferrimagnetic layer F and normal-metal N, spin mediated by (1) spin-polarized conduction electrons and/or (2) torque between electron spins. To identify cross-over from (2), we study laser-driven currents in F|Pt where consists model materials with different degrees electrical conductivity. For magnetic insulators YIG, GIG maghemite,...
The different magnetic and crystallographic structures in the series of ${\mathrm{Tb}}_{5}({\mathrm{Si}}_{x}{\mathrm{Ge}}_{1\ensuremath{-}x}{)}_{4}$ compounds have been studied by means macroscopic (ac susceptibility, linear thermal expansion, resistivity) microscopic neutron powder diffraction experiments. As a result, magnetic-crystallographic temperature-composition phase diagram has determined over whole temperature range (2--300 K). We described detail origin low-temperature transitions...
Large low-field magnetoresistance (LFMR) together with high Curie temperatures (TC) are requirements for some applications in magnetoelectronics. In order to optimize both parameters, we have investigated double perovskites (Ba0.8Sr0.2)2−xLaxFeMoO6 (0⩽x⩽0.4). High-temperature neutron diffraction measurements indicate a strong increase TC La doping (from ≈345 K x=0 ≈405 x=0.4). The LFMR is very large (at 10 KOe≈27% at and ≈7% 290 K) decreases doping. This decrease cannot be attributed...
In order to investigate the paramagnetic ground state of colossal magnetoresistance (CMR) ${\mathrm{Sm}}_{0.55}{\mathrm{Sr}}_{0.45}{\mathrm{MnO}}_{3}$ compound we have used a wide set techniques: magnetoresistance, magnetization, high-resolution neutron diffraction, small-angle and muon spin relaxation. According these measurements would consist \ensuremath{\sim}0.8 nm ferromagnetic clusters embedded in short-range charge/orbital ordered matrix. The CMR effect occurs due percolation clusters.