L. Pérez

Electrodeposited amorphous CoP multilayers with high permeability

Abstract Multilayer films composed of Co x P 1− x ferromagnetic layers with different composition (0.74 x x P 1− x multilayers consisting of magnetic and non-magnetic ( x

Weak-antilocalization signatures in the magnetotransport properties of individual electrodeposited Bi Nanowires

We study the electrical resistivity of individual Bi nanowires of diameter 100 nm fabricated by electrodeposition using a four-probe method in the temperature range 5–300 K with magnetic fields up to 90 kOe. Low-resistance Ohmic contacts to individual Bi nanowires are achieved using a focused ion beam to deposit W-based nanocontacts. Magnetoresistance measurements show evidence for weak antilocalization at temperatures below 10 K, with a phase-breaking length of 100 nm.

Magnetic properties of CoNiFe alloys electrodeposited under potential and current control conditions

Electrodeposited CoNiFe alloys have been produced under potential and current control conditions. It was found that composition, crystalline structure and magnetic properties are the same irrespective of which plating control is used. Magnetic anisotropy is present in the softest samples. A study of the dependence of magnetic properties and domain structure on the thickness of the films is also reported.

Small Fluxgate Magnetometers: Development and Future Trends in Spain

In this paper, we give an overview of the research on fluxgate magnetometers carried out in Spain. In particular we focus in the development of the planar-type instruments. We summarize the fabrication processes and signal processing developments as well as their use in complex systems and space.

Improving the characteristics in magnetostrictive-piezoelectric sensors when the viscous interface is removed

This paper presents the results obtained with a prototype of a magnetostrictive-piezoelectric magnetic sensor where the ferromagnetic material has been grown by sputtering over the piezoelectric support where a copper layer has been previously deposited and electrolitically polished. In this way, the coupling between the piezoelectric and the ferromagnetic materials is stronger than that obtained by using a viscous fluid between both materials, as it is used to be. The most significant advances are the good sensitivity of 0.5 mV/μT for a 1.5-μm-thick ferromagnetic layer and the important reduction of the magnetic hysteresis due to the piezoelectric vibration.

Magnetometric sensors based on planar spiral coils

Abstract By using a combination of sputtering, photolithography, and electrochemical deposition techniques spiral coils with good performances have been grown (low resistance, high number of turns/cm …). This can be used as exciting coils of a magnetic sensor or as a part of a planar inductor.

Growth, structure and magnetism of ε-Fe2O3 in nanoparticle form

We present a novel and easy synthetic path to prepare e-Fe2O3 (∼90%) with a small portion of α-Fe2O3 nanoparticles embedded in an amorphous silica matrix. An exhaustive structural study reveals the higher relative concentration of the e-phase, with an average particle size of 17 nm. Confocal Raman microscopy and X-ray absorption spectroscopy are presented as novel techniques to characterize the e-polymorph. The magnetic properties have been studied in a wide range of temperatures (5–1000 K), detecting blocking effects (∼135 K), collapse effects (50–125 K), Morin (∼268 K) and Neel (∼505 K) transitions.

Epsilon iron oxide: Origin of the high coercivity stable low Curie temperature magnetic phase found in heated archeological materials

The identification of epsilon iron oxide (ɛ-Fe2O3) as the low Curie temperature high coercivity stable phase (HCSLT) carrying the remanence in heated archeological samples has been achieved in samples from two archeological sites that exhibited the clearest evidence of the presence of the HCSLT. This uncommon iron oxide has been detected by Confocal Raman Spectroscopy (CRS) and characterized by rock magnetic measurements. Large numbers of ɛ-Fe2O3 microaggregates (in CO) or isolated clusters (in HEL) could be recognized, distributed over the whole sample, and embedded within the ceramic matrix, along with hematite and pseudobrookite and with minor amounts of anatase, rutile, and maghemite. Curie temperature estimates of around 170°C for CO and 190°C for HEL are lower than for pure, synthetic ɛ-Fe2O3 (227°C). This, together with structural differences between the Raman spectra of the archeologically derived and synthetic samples, is likely due to Ti substitution in the ɛ-Fe2O3 crystal lattice. The γ-Fe2O3-ɛ-Fe2O3-α-Fe2O3 transformation series has been recognized in heated archeological samples, which may have implications in terms of their thermal history and in the factors that govern the formation of ɛ-Fe2O3.

Formation of a magnetite/hematite epitaxial bilayer generated with low energy ion bombardment

We have used a low-energy ion bombardment to fabricate an epitaxial single-crystalline magnetite/hematite bilayer grown on Au(111). This non-conventional fabrication method involves the transformation of the upper layers of a single-crystalline hematite thin film to single-crystalline magnetite, a process driven by the preferential sputtering of oxygen atoms and favoured by the good structural matching of both phases. We show the reversibility of the transformation between hematite and magnetite, always keeping the epitaxial and single-crystalline character of the films. The magnetic characterization of the bilayer grown using this method shows that the magnetic response is mainly determined by the magnetite thin film, exhibiting a high coercivity.

Tuning the magnetic properties of FeCo by pulsed DC magnetron sputtering

We report a comparison of the magnetic properties of Fe53CO47 grown with DC and pulsed DC (PDC) sputtering sources. While no remarkable differences concerning the structure and composition are found, films grown using the PDC source exhibit reduced coercivity by several times compared to the samples grown using the DC source under similar conditions. In addition, PDC films exhibit hard axis rocking effects and a better defined anisotropy axis. By means of EXAFS, we have measured the atomic distances in the FeCo matrix and bcc-Co clusters. We show that the small changes within the FeCo matrix are directly related to the reduction in coercivity. The tuning of these properties by simply choosing the source or the power opens a simple path to tailor the magnetic properties.