Laboratori d'instrumentació física

zip comprimit. Pàgina inicial:161/index.htm[cat] Conté els guions dels 6 treballs de laboratori (corresponents a 3 crèdits) de l'assignatura "Instrumentació Física" (que en té un total de 9) de l'Ensenyament de Física de la Universitat de Barcelona. El temari dels treballs pràctics que es proposa cobreix bé les matèries tractades en l'assignatura, ajudant a l'estudiant en la seva comprensió, i fent possible que l'alumne manegui físicament aquells dispositius que estudia en les classes de teoria.[eng] Includes the guidebook for the 6 laboratory works (corresponding to 3 credits) of the course "Physical Instrumentation" (with a total amount of 9) of the Degree o Physics of the Barcelona University. The proposed program of practical works covers the contents of the course, assisting the students in their understanding, as well as allowing them handling the devices and equipments studied in the theory classes.[spa] Muestra los guiones de los 6 trabajos de laboratorio (correspondientes a 3 créditos) de la asignatura "Instrumentación Física" (que en total tiene 9) de la titulación de Física de la Universidad de Barcelona. El temario de los trabajos prácticos que se proponen cubre bien las materias tratadas en la asignatura, ayudando al estudiante en su comprensión, y haciendo posible que el alumno maneje físicamente aquellos dispositivos que estudia en las clases de teoría

Structure and magnetic properties of Sm/Fe multilayers versus substrate temperature

Three Sm(2 Å)/Fe(3 Å) multilayers have been made using two electron beams in a high vacuum chamber onto very thin Kapton foils at different substrate temperatures, (Ts=40°C, 150°C and 230°C), with the same total thickness of 3000 Å. We have found that the substrate temperature strongly affects structure and magnetic properties of the samples. For a substrate temperature of 150°C the sample behaves as a three dimensional random magnet

Strain tuned magnetoelectric coupling in orthorhombic YMnO3 thin films

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.Orthorhombic YMnO3epitaxialthin films were grown on Nb(0.5%)-doped SrTiO3(001) substrates. Film's thickness was varied to tune the epitaxial strain. Structural and magnetic properties are well correlated, presenting a more pronounced ferromagnetic behavior as the unit cell becomes more distorted. Dielectric properties were investigated as a function of the temperature and magnetic field. The dielectric peak occurring at temperatures below the antiferromagnetic ordering is proved to be magnetoelectric and its amplitude is dependent on the unit cell distortion. These findings allow tailoring ferromagnetic and magnetoelectric properties via epitaxial strain

Electric field control of exchange bias in multiferroic epitaxial heterostructures

The magnetic exchange bias between epitaxial thin films of the multiferroic (antiferromagnetic and ferroelectric) hexagonal YMnO3 oxide and a soft ferromagnetic (FM) layer is used to couple the magnetic response of the ferromagnetic layer to the magnetic state of the antiferromagnetic one. We will show that biasing the ferroelectric YMnO3 layer by an appropriate electric field allows modifying and controlling the magnetic exchange bias and subsequently the magnetotransport properties of the FM layer. This finding may contribute to pave the way towards a new generation of electric-field controlled spintronics devices.Comment: 15 pages, 5 figures, submitte

Emergence of ferromagnetism in antiferromagnetic TbMnO3 by epitaxial strain

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.We show that in oxide thin films of spiral antiferromagnetic orthorhombic TbMnO3, ferromagnetism emerges resulting from epitaxially induced strain. The unit cell volume can be tuned (contracting up to a 2%) by varying thickness and deposition conditions; it is found that the ferromagnetic response correlates with the unit cell deformation. Such effect of strain on the magnetic properties turns out to be similar to that occurring in collinear orthorhombic antiferromagnets such as YMnO3. Owing to the intimate relationship between magnetic order and ferroelectricity in TbMnO3 these results may provide a new route to induce magnetoelectric coupling and tailor their ferroelectric response

Dielectric characterization of multiferroic magnetoelectric double-perovskite Y(Ni0.5Mn0.5)O3 thin films

We report on functional properties of Y(Ni0.5Mn0.5)O3 epitaxial thin films, growth by pulsed laser deposition, observing clear features of its ferroelectric and ferromagnetic nature at cryogenic temperature. Temperature-dependent complex impedance spectroscopy (IS) characterization has shown a dielectric anomaly around the ferromagnetic Curie temperature ( 100 K) indicative of coupling between magnetic and electric orders

High-temperature magnetodielectric Bi(Fe0.5Mn0.5)O3 thin films with checkerboard-ordered oxygen vacancies and low magnetic damping

The possibility of affecting the magnetic properties of a material by dielectric means, and vice versa, remains an attractive perspective for modern electronics and spintronics. Here, we report on epitaxial Bi(Fe0.5Mn0.5)O3 thin films with exceptionally low Gilbert damping and magnetoelectric coupling above room temperature (<400 K). The ferromagnetic order, not observed in bulk, has been detected with a total magnetization of 0.44 μB/formula units with low Gilbert damping parameter (0.0034), both at room temperature. Additionally, a previously overlooked check-board ordering of oxygen vacancies is observed, providing insights on the magnetic and dielectric origin of the multifunctional properties of the films. Finally, intrinsic magnetodielectric behavior is observed as revealed by the variation of dielectric permittivity well above room temperature. These findings show the possibility of electric-field-controlled magnetic properties, in low Gilbert-damping-based spintronic devices, using single-phase multiferroic material

La llicenciatura en Física: Perfil de la professió. Estudi d’inserció professional

Les oportunitats professionals dels llicenciats i llicenciades en Física han evolucionat molt en el passat immediat, i també s’ha ampliat els tipus de sectors laborals que enrolen físics. Fa just trenta anys, la major part dels titulats era absorbida pel sector de l’ensenyament secundari i superior. Una minoria aconseguia fer carrera de recerca, principalment en centres acadèmics. En l’actualitat el panorama ha canviat força ja que, com revelen algunes enquestes a graduats recents de mitjan els anys noranta, la sortida professional de l’ensenyament només representava un 50 % del total

Kerr measurements on single-domain SrRuO3 thin films

We report on the magneto-optical measurements of an epitaxial SrRuO3 film grown on SrTiO3 (0 0 1), which previously was determined to be single domain orientated by x-ray diffraction and Raman spectroscopy techniques. Our experiments reveal a large Kerr rotation, which reaches a maximum value of about 0.5° at low temperature. By measuring magnetic hysteresis loops at different temperatures, we determined the temperature dependence of the Kerr rotation in the polar configuration. Values of the anisotropic magnetoresistance ~ 20% have been measured. These values are remarkably higher than those of other metallic oxides such as manganites. This striking difference can be attributed to the strong spin-orbit interaction of the Ru 4d ion in the SrRuO3 compound

Epitaxial growth of biferroic YMnO3(0001) on platinum electrodes

Epitaxial films of the biferroic YMnO3 (YMO) oxide have been grown on platinum-coated SrTiO3(1 1 1) and Al2O3(0 0 0 1) substrates. The platinum electrodes, (1 1 1) oriented, are templates for the epitaxy of the hexagonal phase of YMO with a (0 0 0 1) out-of-plane orientation, which is of interest as this is the polarization direction of YMO. X-ray diffractometry indicates the presence of two crystal domains, 60° rotated in-plane, in the Pt(1 1 1) layers which subsequently are transferred on the upperlaying YMO. Cross-section analysis by high-resolution transmission electron microscopy (HRTEM) of YMnO3/Pt/SrTiO3(1 1 1) shows high-quality epitaxy and sharp interfaces across the structure in the observed region. We present a detailed study of the epitaxial growth of the hexagonal YMO on the electrodes