Open Access
High magnetic, transport, and optical uniaxial anisotropis generated by controlled directionally grown nano-sheets in Fe thin films
(American Institute of Physics, 2023) Favieres Ruiz, Cristina; Vergara Platero, José; Madurga Pérez, Vicente; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
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 (IReflmax–IReflmin)/IReflmax of the intensity of reflected light by the films reached up to 61% for 34 nm thick samples, achieving the maximum value, IReflmax, when the plane of the incident light coincided with the direction of the nano-sheets and the minimum, IReflmin, when this plane was perpendicular to the direction of the nano-sheets. The origin of these anisotropic behaviors was established. These anisotropic films with high magnetization and high uniaxial anisotropies at the nanoscale can be useful for microelectronics applications, for devices such as magnetic sensors and transducers, or for ultrahigh frequency inductors
Open Access
Influence of bi content on the temperature of the formation of the hard magnetic MnBi phase: simultaneous irreversible drop of resistance
(MDPI, 2022) Vergara Platero, José; Favieres Ruiz, Cristina; Madurga Pérez, Vicente; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias
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.
Open Access
Magnetic domain configurations of pulsed laser deposited MnBi hard magnetic films
(Elsevier, 2022) Madurga Pérez, Vicente; Favieres Ruiz, Cristina; Vergara Platero, José; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
Hard magnetic MnBi films were obtained by appropriate heat treatments of pulsed laser deposited (PLD) (Bi/Mn) films. X-ray diffraction patterns indicated a slight texture of MnBi crystallites and magnetometry measurements showed a slight preferential growth of the crystallites with their c-axis perpendicular to the film plane. Magnetic force microscopy (MFM) measurements displayed the presence of magnetic domains, whose size was in the micrometer range, and which were correlated to the MnBi grains observed in the sample. The addition of extra Mn layers did not modify significantly the previous structural and magnetic results. Nevertheless, the size of the magnetic domains increased to a few microns. However, on adding extra Bi layers, upon annealing, the MnBi grains grew with their c-axes perpendicular to the film plane. A perpendicular to the film magnetic anisotropy was deduced from the hysteresis loops, where an increase in the remanence of the magnetization was measured when the magnetic field was applied perpendicular to the film plane. In these samples, by measuring the magnetic domain configuration of the samples by MFM, we observed that the size of the magnetic domains exceeded the dimensions of the grains. This change in the magnetic structure of the films was assumed to be due to the coupling of the magnetization in the neighboring grains, and it was responsible for the decrease of the coercivity in the Bi rich samples.
Open Access
Tailoring magnetic and transport anisotropies in Co100−x –Cux thin films through obliquely grown nano-sheets
(MDPI, 2022) Favieres Ruiz, Cristina; Vergara Platero, José; Madurga Pérez, Vicente; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
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 x increased, from 200 (x = 0) to 1100 Am−1 (x = 30). In contrast, in obliquely deposited films, Hc decreased from 1500 (x = 0) to 100 Am−1 (x = 30) as x increased. Activation energy spectra corresponding to structural relaxation phenomena in obliquely deposited films were obtained from transport property measurements. They revealed two peaks, which also depended on their nano-morphology and composition.

Vergara Platero, José

Email Address

person.page.identifierURI

Birth Date

Job Title

Last Name

First Name

person.page.departamento

person.page.instituteName

ORCID

person.page.observainves

person.page.upna

Name

Filters

Author

Subject

Date

Has files

Item Type

Type

Settings

Sort By

Results per page

Search Results