Cristina Favieres | Public University of Navarre (original) (raw)

Papers by Cristina Favieres

AIP advances, Feb 1, 2024

Journal of Applied Physics

Fe films with thicknesses between 17 and 95 nm were grown with a nano-sheet morphology, which ena... more Fe films with thicknesses between 17 and 95 nm were grown with a nano-sheet morphology, which enabled their high uniaxial magnetic, transport, and optical in-plane anisotropies. The top edge of the nano-sheets was directly visualized as nano-string-like structures of approximately 12.5–14 nm width and 100–300 nm length. The hysteresis loops showed a clear easy direction of magnetization in the longitudinal direction of the nano-sheets, whereas the hard direction loops were anhysteretic, with no remanence and zero coercive field. The anisotropy field exhibited values between 70 and 111 kA/m depending on the thickness of the films, with the maximum value corresponding to a 34 nm thick sample. The resistance of the films was also found to be highly anisotropic. The ratio (R⊥–R||)/R|| was ≈86%, with R|| and R⊥ being the resistances in the parallel and perpendicular directions of the nano-sheets, respectively. Likewise, the reflectivity of the samples behaved anisotropically; the ratio (...

Non-Crystalline and Nanoscale Materials, 1998

Magnetochemistry

Pulsed laser-deposited (PLD) MnBi films were fabricated by alternating deposition of Mn and Bi la... more Pulsed laser-deposited (PLD) MnBi films were fabricated by alternating deposition of Mn and Bi layers. In order to obtain the ferromagnetic MnBi phase, heat treatments were performed on the samples. Simultaneously, the resistance of the samples was monitored as a function of the temperature. Thus, on increasing the temperature, a steep decrease in the resistance of the films was observed, simultaneous to the onset of the formation of the MnBi phase. At room-temperature, these annealed samples showed a ferromagnetic behavior, as well as the presence of the characteristic LT-MnBi phase diffraction peaks in the X-ray diffraction patterns. The temperature of the generation of the MnBi phase depended on the relative concentration of Mn and Bi in the different samples: on increasing the Bi atomic concentration, the temperature of the generation of the MnBi phase decreased.

Magnetochemistry, 2021

The magnetic and transport properties of pulsed laser-deposited Co100−x–Cux thin films were tailo... more The magnetic and transport properties of pulsed laser-deposited Co100−x–Cux thin films were tailored through their nano-morphology and composition by controlling for the deposition geometry, namely normal or oblique deposition, and their Cu content. All films were composed of an amorphous Co matrix and a textured growth of Cu nanocrystals, whose presence and size d increased as x increased. For x = 50, all films were superparamagnetic, regardless of deposition geometry. The normally deposited films showed no in-plane magnetic anisotropy. On the contrary, controllable in-plane uniaxial magnetic anisotropy in both direction and magnitude was generated in the obliquely deposited films. The magnetic anisotropy field Hk remained constant for x = 0, 5 and 10, Hk ≈ 35 kAm−1, and decreased to 28 and 26 kAm−1 for x = 20 and 30, respectively. This anisotropy had a magnetostatic origin due to a tilted nano-sheet morphology. In the normally deposited films, the coercive field Hc increased when ...

Journal of Alloys and Compounds

Journal of Magnetism and Magnetic Materials, 2022

Journal of Alloys and Compounds, 2016

Abstract Thin films of Co-rich transition metal or metal Co–MT (MT = V, Cr, Cu, Zn, Cd, Hf) compo... more Abstract Thin films of Co-rich transition metal or metal Co–MT (MT = V, Cr, Cu, Zn, Cd, Hf) compounds were fabricated as a superposition of oblique nano-sheets (≈300 x 80 × 5 nm for each nano-sheet) from a mixture of Co and MT plasmas. Because the X-ray diffraction patterns of all of the films showed a similar nano-crystalline microstructure, the oblique nano-sheets were visualized by high-resolution transmission electron microscopy. This nano-morphology generated strong in-plane uniaxial magnetic anisotropy, UMA, as we explained in this work, for all the as-deposited films. The evolution of this magnetic anisotropy was studied at temperatures up to 450 °C. Three different cases were observed after these heat treatments depending on the MT component of the film: (1) UMA was lost for temperatures ≈ 400 °C, (2) UMA retained the same value until the highest temperature was reached, or (3) UMA was enhanced by a factor greater than 2 for the highest temperature. This behavior can be explained by considering of the various processes of structural relaxation and crystallization produced by heat treatment and affected by the nano-sheet morphology.

Journal of Physics D: Applied Physics, 2015

Key Engineering Materials, 2015

Thin films of Co-Hf (≈ 86-14 % at.) were grown over Si micro-cantilevers using a glancing-angle d... more Thin films of Co-Hf (≈ 86-14 % at.) were grown over Si micro-cantilevers using a glancing-angle deposition technique. A controlled easy direction of magnetisation (anisotropy field μoHk ≈ 0.1 T) in the longitudinal or in the transverse direction of the micro-cantilevers was generated. The mechanical properties of the films under the action of a magnetic field were opposite depending on the magnetisation’s easy direction: i) their deflection was either zero or the maximum value depending on the direction of the applied magnetic field with respect to the parallel or transverse easy direction of magnetisation; ii) the shift in the resonance frequency under a longitudinal or transverse magnetic field was also different depending on the longitudinal or transverse easy direction of magnetisation. The use of these coated devices with micromagnet-like films for sensors and transducers is discussed.

Nanotechnology, 2010

Si micro-cantilevers were coated with Co nano-strings, which were simultaneously grown and sculpt... more Si micro-cantilevers were coated with Co nano-strings, which were simultaneously grown and sculpted during off-normal pulsed laser deposition. The surface morphology of micro-cantilevers with longitudinal or transverse nano-strings was analysed by scanning tunnelling microscopy. Magnetic anisotropy was detected with a magnetization direction parallel to the nano-strings. The two micro-cantilever types exhibited different mechanical behaviours when placed in a non-uniform magnetic field. By varying the relative position of the micro-cantilever with respect to the gradient direction of this field, a split in the resonant frequency shift of the micro-cantilevers was generated, depending on the direction of magnetic anisotropy. Discrimination was achieved between the micro-cantilevers with transverse nano-strings and the micro-cantilevers with longitudinal nano-strings. The lowest limit of magnetic moment for distinction between these covered micro-cantilevers was 10(-8) emu. The possible benefits of these magneto-mechanical properties for the biological, chemical and physical applications of some nano-mechanical devices are pointed out.

MRS Proceedings, 1996

ABSTRACTElectrolytic cylindrical amorphous CoP multilayers, grown on copper wires, with controlle... more ABSTRACTElectrolytic cylindrical amorphous CoP multilayers, grown on copper wires, with controlled continuos variation of the magnetic anisotropy, in both, direction and magnitude, have been produced. The inner zone of the samples has been grown to exhibit radial anisotropy and the overlayer has been obtained with planar longitudinal anisotropy. Our studies have revealed that the magnetization at the surface of the samples is strongly coupled with the bulk anisotropy for thickness of the overlayer of ≈ 1.5 μm. Furthermore, it has been found that an angular deformation applied to the samples, when the copper wire is subjected to a torsion, modifies the direction of the longitudinal anisotropy to the helical direction. Also, a large spontaneous Matteucci effect is induced by means of this angular deformation.

MRS Proceedings, 1999

ABSTRACTPlanar and cylindrical Co thin films have been obtained by pulsed laser ablation. X-ray d... more ABSTRACTPlanar and cylindrical Co thin films have been obtained by pulsed laser ablation. X-ray diffractograms have shown no crystalline structure for the as-deposited samples, while the 450 °C annealed samples exhibit Co fcc crystalline peaks. The Scanning Tunnelling Microscopy has revealed a small increase of the surface roughness for the annealed films. The Hall effect has been used to determine the value of the spontaneous magnetization, Ms, at room temperature; Ms, = 14 kgauss for the as-deposited sample and Ms, = 17.6 kgauss for the 450 °C annealed sample. From transverse magnetooptic Kerr effect, it has been found that the as-deposited samples exhibit magnetic bistability, with a coercive field, Hc, = 6 0e. The annealed samples also show a bistable behavior until the annealing temperature is 450 °C. Besides, it has been observed an increase of Hc up to = 50 Oe, when the annealing temperature increases. The vibrating sample magnetometry has confirmed these results, showing tha...

Journal of Physics: Condensed Matter, 2013

The magnetic domain configurations of soft magnetic, nanostructured, pulsed laser-deposited Co fi... more The magnetic domain configurations of soft magnetic, nanostructured, pulsed laser-deposited Co films were investigated. Their dependence on both the thickness t (20 nm ≤ t ≤ 200 nm) and the anisotropy was studied. Charged zigzag walls, with a characteristic saw-tooth vertex angle θ, were observed. θ changed with t from θ ≈ 17° to ≈25°, presenting an intermediate sharp maximum that has not been described before. The reduced length of the zigzag walls also exhibited a peak at t ≈ 70 nm. The relationship between the total reduced length and the density energy of the magnetic wall allowed us to establish a change from a Néel-type to a Bloch-type core of the zigzag walls at this thickness, t ≈ 70 nm. We also accounted for the magnetic energy arising from the surface roughness of the thinner films after imaging the film surface morphologies. Moreover, this distinctive behaviour of the zigzag walls of these low-anisotropy films was compared to that of high-anisotropy films.

Materials Science Forum, 2009

Ni 2 MnGa thin films, with thickness between 30 and 60 nm, were pulsed-laser deposited at room te... more Ni 2 MnGa thin films, with thickness between 30 and 60 nm, were pulsed-laser deposited at room temperature on Si micro-cantilevers and glass substrates. Two different deposition processes were performed: normal deposition and off-normal. After annealing in an inert atmosphere, in-plane isotropic magnetic hysteresis loops were measured for the normal deposited films. In contrast, in-plane anisotropic hysteresis loops were obtained from the off-normal deposited ones. An in-plane easy direction for the magnetisation, perpendicular to the incidence plane of the plasma during deposition, was measured with an anisotropy field of ≈100 Oe and an easy coercive field of ≈24 Oe. The mechanical behaviour of the magnetically anisotropic coated micro-cantilevers and their response to a decreasing temperature permitted observing the martensitic transformation of the Ni 2 MnGa thin films.

The component part is provided here to allow users access to individually authored sections f pro... more The component part is provided here to allow users access to individually authored sections f proceedings, annals, symposia, etc. However, the component should be considered within [he context of the overall compilation report and not as a stand-alone technical report. The following component part numbers comprise the compilation report: ADP012260 thru ADP012329

Se han obtenido capas y multicapas de CoP electrodepositado con propiedades magneticas predetermi... more Se han obtenido capas y multicapas de CoP electrodepositado con propiedades magneticas predeterminadas y geometria plana y cilindrica. Se ha generado una anisotropia magnetica de valor continuo y controlado desde la direccion perpendicular al plano (o superficie cilindrica) a la contenida en el mismo. Se ha utilizado la tecnica BITTER, el efecto KERR magnetooptico y el metodo de induccion para estudiar su comportamiento magnetico y establecer el valor y direccion de esta anisotropia controlada. Se ha propuesto un modelo fenomenologico que explica este comportamiento. Para las muestras cilindricas, ademas, se ha estudiado un efecto MATTEUCCI espontaneo y, al controlar la magnitud del mismo, se presenta su potencial como elementos activos de sensores. Se ha estudiado su magnetoimpedancia, MI, y su dependencia con la torsion. Los altos valores de esta MI se presentan paralelos y ligados a los de su efecto WIEDEMANN inverso. El seguimiento, por tecnica BITTER, de los cambios de la estru...

Materials

Charged magnetic domain walls have been visualized in soft magnetic nanostructured Fe thin films ... more Charged magnetic domain walls have been visualized in soft magnetic nanostructured Fe thin films under both static and dynamic conditions. A transition in the core of these zigzagged magnetic walls from Néel-type to Bloch-type through the formation of crosstie walls has been observed. This transition in charged zigzagged walls was not previously shown experimentally in Fe thin films. For film thicknesses t < 30 nm, Néel-type cores are present, while at t ≈ 33 nm, walls with crosstie cores are observed. At t > 60 nm, Bloch-type cores are observed. Along with the visualization of these critical parameters, the dependence on the film thickness of the characteristic angle and length of the segments of the zigzagged walls has been observed and analyzed. After measuring the bistable magneto-optical behavior, the values of the wall nucleation magnetic field and the surface roughness of the films, an energetic fit to these nucleation values is presented.

Journal of Magnetism and Magnetic Materials