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1.
Nat Mater ; 18(8): 840-845, 2019 08.
Artículo en Inglés | MEDLINE | ID: mdl-31110346

RESUMEN

Large changes in the magnetization of ferromagnetic films can be electrically driven by non-180° ferroelectric domain switching in underlying substrates, but the shear components of the strains that mediate these magnetoelectric effects have not been considered so far. Here we reveal the presence of these shear strains in a polycrystalline film of Ni on a 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 substrate in the pseudo-cubic (011)pc orientation. Although vibrating sample magnetometry records giant magnetoelectric effects that are consistent with the hitherto expected 90° rotations of a global magnetic easy axis, high-resolution vector maps of magnetization (constructed from photoemission electron microscopy data, with contrast from X-ray magnetic circular dichroism) reveal that the local magnetization typically rotates through smaller angles of 62-84°. This shortfall with respect to 90° is a consequence of the shear strain associated with ferroelectric domain switching. The non-orthogonality represents both a challenge and an opportunity for the development and miniaturization of magnetoelectric devices.

2.
Phys Rev Lett ; 117(14): 147201, 2016 Sep 30.
Artículo en Inglés | MEDLINE | ID: mdl-27740785

RESUMEN

We report a spin valve with a few-layer graphene flake bridging highly spin-polarized La_{0.67}Sr_{0.33}MnO_{3} electrodes, whose surfaces are kept clean during lithographic definition. Sharp magnetic switching is verified using photoemission electron microscopy with x-ray magnetic circular dichroism contrast. A naturally occurring high interfacial resistance ∼12 MΩ facilitates spin injection, and a large resistive switching (0.8 MΩ at 10 K) implies a 70-130 µm spin diffusion length that exceeds previous values obtained with sharp-switching electrodes.

3.
Sci Rep ; 5: 10026, 2015 May 13.
Artículo en Inglés | MEDLINE | ID: mdl-25969926

RESUMEN

Ferroic materials (ferromagnetic, ferroelectric, ferroelastic) usually divide into domains with different orientations of their order parameter. Coupling between different ferroic systems creates new functionalities, for instance the electrical control of macroscopic magnetic properties including magnetization and coercive field. Here we show that ferroelastic domains can be used to control both magnetic order and magnetization direction at the nanoscale with a voltage. We use element-specific X-ray imaging to map the magnetic domains as a function of temperature and voltage in epitaxial FeRh on ferroelastic BaTiO3. Exploiting the nanoscale phase-separation of FeRh, we locally interconvert between ferromagnetic and antiferromagnetic states with a small electric field just above room temperature. Imaging and ab initio calculations show the antiferromagnetic phase of FeRh is favoured by compressive strain on c-oriented BaTiO3 domains, and the resultant magnetoelectric coupling is larger and more reversible than previously reported from macroscopic measurements. Our results emphasize the importance of nanoscale ferroic domain structure and the promise of first-order transition materials to achieve enhanced coupling in artificial multiferroics.

4.
Nat Mater ; 13(4): 345-51, 2014 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-24464245

RESUMEN

Controlling magnetism by means of electric fields is a key issue for the future development of low-power spintronics. Progress has been made in the electrical control of magnetic anisotropy, domain structure, spin polarization or critical temperatures. However, the ability to turn on and off robust ferromagnetism at room temperature and above has remained elusive. Here we use ferroelectricity in BaTiO3 crystals to tune the sharp metamagnetic transition temperature of epitaxially grown FeRh films and electrically drive a transition between antiferromagnetic and ferromagnetic order with only a few volts, just above room temperature. The detailed analysis of the data in the light of first-principles calculations indicate that the phenomenon is mediated by both strain and field effects from the BaTiO3. Our results correspond to a magnetoelectric coupling larger than previous reports by at least one order of magnitude and open new perspectives for the use of ferroelectrics in magnetic storage and spintronics.

5.
Nat Mater ; 12(1): 52-8, 2013 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-23104152

RESUMEN

Large thermal changes driven by a magnetic field have been proposed for environmentally friendly energy-efficient refrigeration, but only a few materials that suffer hysteresis show these giant magnetocaloric effects. Here we create giant and reversible extrinsic magnetocaloric effects in epitaxial films of the ferromagnetic manganite La(0.7)Ca(0.3)MnO(3) using strain-mediated feedback from BaTiO(3) substrates near a first-order structural phase transition. Our findings should inspire the discovery of giant magnetocaloric effects in a wide range of magnetic materials, and the parallel development of nanostructured bulk samples for practical applications.

6.
Ann Pharmacother ; 33(5): 623-30, 1999 May.
Artículo en Inglés | MEDLINE | ID: mdl-10369628

RESUMEN

BACKGROUND: Clozapine has recently been found to be associated with neuroleptic malignant syndrome (NMS). Our objective is to determine if clozapine causes NMS, if the presentation of clozapine-induced NMS differs from that of traditional agents, and which set of diagnostic criteria will most readily allow diagnosis of NMS associated with clozapine. METHODS: Two new cases of clozapine-associated NMS are presented, along with previously reported cases from the literature, identified by using a MEDLINE search (1966-August 1998). From all cases, concomitant medications and washout periods were examined (if available) to assess clozapine as the likely cause of NMS. Characteristics of clozapine and traditional antipsychotic-induced NMS were compared. Different diagnostic criteria for NMS were applied to the cases to determine which were more likely to diagnose the syndrome. RESULTS: Clozapine was deemed a highly probable cause of NMS in 14 cases, a medium probability cause in five cases, and a low probability cause in eight cases. The most commonly reported clinical features were tachycardia, mental status changes, and diaphoresis. Fever, rigidity, and elevated creatine kinase were less prominent than in NMS associated with classical neuroleptics. CONCLUSIONS: Clozapine appears to cause NMS, although the presentation may be different than that of traditional antipsychotics. Levenson's original and Addonizio's modified criteria were more likely to diagnose NMS than were other criteria. Clozapine-associated NMS may present with fewer clinical features. Limitations are the lack of detailed information provided by many of the case reports and the use of "modified" diagnostic criteria for retrospective diagnosis.


Asunto(s)
Antipsicóticos/efectos adversos , Clozapina/efectos adversos , Síndrome Neuroléptico Maligno/etiología , Adulto , Interacciones Farmacológicas , Femenino , Humanos , Masculino , Persona de Mediana Edad , Síndrome Neuroléptico Maligno/diagnóstico , Síndrome Neuroléptico Maligno/epidemiología , Esquizofrenia/diagnóstico
7.
Appl Opt ; 21(20): 3702-5, 1982 Oct 15.
Artículo en Inglés | MEDLINE | ID: mdl-20396302

RESUMEN

An optical correlation technique has been shown to accurately measure leak conduction rates from 10(-1) to 10(-6) atm cc/sec. Using hybrid microcircuit packages with glass capillary leakers, dimensional changes were detected as the packages were exposed to a small increase in external pressure. The rate at which the package returns to its original dimensions is measured and used, along with the internal free volume, to compute the leak rate. Because of its several advantages, the technique has the potential to become a useful nondestructive quality-control technique.

8.
Med Instrum ; 14(5): 264-6, 1980.
Artículo en Inglés | MEDLINE | ID: mdl-7453600

RESUMEN

An interlaboratory comparison of test results on a common set of electrosurgical devices showed power measurements varied as much as 30%. The primary source of this variation is the reactances in the patient cables used to couple the output of the device to the standard test loads. Transmission line theory predicts, and empirical results demonstrate, that power measurement variation can be reduced by matching cable impedances to test loads or by using cables that are sufficiently short to minimize cable reactances.


Asunto(s)
Electrocirugia/instrumentación , Conductividad Eléctrica , Electrónica Médica/normas , Humanos , Control de Calidad
9.
Heredity (Edinb) ; 44(2): 251-68, 1980 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-6771236

RESUMEN

Fifteen highly inbred lines extracted by sib-mating from the laboratory cage population, "Texas", of Drosophila melanogaster were crossed in a half-diallel mating design. Female progeny were assayed individually for ADH activity at 25 degrees and 35 degrees C and for total protein. At 25 degrees C there was considerable additive genetical variation and the dominance variation was attributable to specific parents and to specific crosses at random in the diallel table. The character total protein also showed considerable additive variation but less dominance variation. Largely independent gene action was shown by the characters ADH activity and total protein. There were strong genotype-environment interactions for heat-stability. At 35 degrees C most of the genetical variation was additive and mainly due to modifier loci. It was concluded that at 25 degrees C dominance was ambidirectional and almost complete. This genetical architecture was compatible with a past history of stabilising selection for ADH activity in the "Texas" population.


Asunto(s)
Oxidorreductasas de Alcohol/genética , Drosophila melanogaster/enzimología , Genes , Variación Genética , Animales , Cruzamientos Genéticos , Femenino , Genotipo , Calor , Cinética , Masculino , Especificidad de la Especie
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