67 research outputs found
Observation of huge thermal spin currents in magnetic multilayers
Thermal spin pumping constitutes a novel mechanism for generation of spin
currents; however their weak intensity constitutes a major roadblock for its
usefulness. We report a phenomenon that produces a huge spin current in the
central region of a multilayer system, resulting in a giant spin Seebeck effect
in a structure formed by repetition of ferromagnet/metal bilayers. The result
is a consequence of the interconversion of magnon and electron spin currents at
the multiple interfaces. This work opens the possibility to design thin film
heterostructures that may boost the application of thermal spin currents in
spintronics
Exploring Recollection and Familiarity Impairments in Parkinson´s disease
There is conflicting evidence on whether patients diagnosed with Parkinson's disease (PD) have cognitive deficits associated with episodic memory and particularly with recognition memory. The aim of the present study was to explore whether PD patients exhibit deficits in recollection and familiarity, the two processes involved in recognition. A sample of young healthy participants (22) was tested to verify that the experimental tasks were useful estimators of recognition processes. Two further samples ¿ one of elderly controls (16) and one of PD patients (20) ¿ were the main focus of this research. All participants were exposed to an associative recognition task aimed at estimating recollection followed by a two-alternative forced-choice (2AFC) test designed to estimate familiarity. The analyses showed a deficit in associative recognition in PD patients and no difference between elderly controls and PD patients in the 2AFC test. By contrast, young healthy participants were better than elderly controls and PD patients in both components of recognition. Further analyses of results of the 2AFC test indicated that the measure chosen to estimate conceptual familiarity was adequate
On the nature of the (de)coupling of the magnetostructural transition in ErSi
In this report, a successful thermodynamical model was employed to understand
the structural transition in ErSi, able to explain the decoupling of
the magnetic and structural transition. This was achieved by the DFT
calculations which were used to determine the energy differences at 0 K, using
a LSDA+U approximation. It was found that the M structure as the stable phase
at low temperatures as verified experimentally with a 0.262 eV.
Finally, it was achieved a variation of Seebeck coefficient ( 6 V)
at the structural transition which allow to conclude that the electronic
entropy variation is negligible in the transition.Comment: 17 pages, 3 figures, 1 tabl
Spin-phonon coupling in epitaxial Sr0.6Ba0.4MnO3 thin films
Spin-phonon coupling is investigated in epitaxially strained Sr1-xBaxMnO3 thin films with perovskite structure by means of microwave (MW) and infrared (IR) spectroscopy. In this work we focus on the Sr0.6Ba0.4MnO3 composition grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate. The MW complex electromagnetic response shows a decrease in the real part and a clear anomaly in the imaginary part around 150 K. Moreover, it coincides with a 17% hardening of the lowest-frequency polar phonon seen in IR reflectance spectra. In order to further elucidate this phenomenon, low-energy muon-spin spectroscopy was carried out, signaling the emergence of antiferromagnetic order with Néel temperature (TN) around 150 K. Thus, our results confirm that epitaxial Sr0.6Ba0.4MnO3 thin films display strong spin-phonon coupling below TN, which may stimulate further research on tuning the magnetoelectric coupling by controlling the epitaxial strain and chemical pressure in the Sr1-xBaxMnO3 system
Ambipolar gate effect and low temperature magnetoresistance of ultrathin La0.8Ca0.2MnO3 Films
Ultrathin La0.8Ca0.2MnO3 films have been measured in a field-effect geometry.
The electric field due to the gate produces a large ambipolar decrease in
resistance at low temperatures. This is attributed to the development of a
pseudogap in the density of states and the couple of localized charge to
strain. The gate effect and mangetoresistance are interpreted in a consistent
framework. The implications for the low temperature behavior of a manganite
film in the two dimensional limit are discussed.Comment: 4 pages, 3 figure
Antiferromagnet-ferromagnet phase transition in lightly doped manganites
Magnetic and structural phase diagrams of the La₀.₈₈MnOx, La₁₋xSrx(Mn₁₋x/₂Nbx/₂)O₃,
Nd₁₋xCaxMnO₃, and Bi₁₋xCaxMnO₃ series constructed on the basis of x-ray, neutron powder diffraction,
Young’s modulus, magnetization and resistivity measurements are presented. It is shown
that the main factor controlling the antiferromagnet–ferromagnet phase transition in the manganites
is a type of an orbital state. The results are discussed in the framework of structurally driven
magnetic phase separation model
Terahertz Spin Currents and Inverse Spin Hall Effect in Thin-Film Heterostructures Containing Complex Magnetic Compounds
Terahertz emission spectroscopy (TES) of ultrathin multilayers of magnetic and
heavy metals has recently attracted much interest. This method not only
provides fundamental insights into photoinduced spin transport and spin–orbit
interaction at highest frequencies, but has also paved the way for
applications such as efficient and ultrabroadband emitters of terahertz (THz)
electromagnetic radiation. So far, predominantly standard ferromagnetic
materials have been exploited. Here, by introducing a suitable figure of
merit, we systematically compare the strength of THz emission from X/Pt
bilayers with X being a complex ferro-, ferri- and antiferromagnetic metal,
that is, dysprosium cobalt (DyCo5), gadolinium iron (Gd24Fe76), magnetite
(Fe3O4) and iron rhodium (FeRh). We find that the performance in terms of
spin-current generation not only depends on the spin polarization of the
magnet’s conduction electrons, but also on the specific interface conditions,
thereby suggesting TES to be a highly interface-sensitive technique. In
general, our results are relevant for all applications that rely on the
optical generation of ultrafast spin currents in spintronic metallic
multilayers
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Terahertz spin currents and inverse spin Hall effect in thin-film heterostructures containing complex magnetic compounds
Terahertz emission spectroscopy (TES) of ultrathin multilayers of magnetic and heavy metals has recently attracted much interest. This method not only provides fundamental insights into photoinduced spin transport and spin–orbit interaction at highest frequencies, but has also paved the way for applications such as efficient and ultrabroadband emitters of terahertz (THz) electromagnetic radiation. So far, predominantly standard ferromagnetic materials have been exploited. Here, by introducing a suitable figure of merit, we systematically compare the strength of THz emission from X/Pt bilayers with X being a complex ferro-, ferri- and antiferromagnetic metal, that is, dysprosium cobalt (DyCo5), gadolinium iron (Gd24Fe76), magnetite (Fe3O4) and iron rhodium (FeRh). We find that the performance in terms of spin-current generation not only depends on the spin polarization of the magnet’s conduction electrons, but also on the specific interface conditions, thereby suggesting TES to be a highly interface-sensitive technique. In general, our results are relevant for all applications that rely on the optical generation of ultrafast spin currents in spintronic metallic multilayers
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