P. Sánchez

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

Magnetostrictive-piezoelectric magnetic sensor with current excitation

A new working configuration for magnetostrictive-piezoelectric magnetic sensors is presented. In this configuration, the excitation is caused using an electrical current flowing through the ferromagnetic sample and the induced signal is sensed in the piezoelectric support as an electrical voltage. This new idea allows a magnetic field detection without any coil and opens a possibility for a future miniaturisation of the sensor.

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.

Domain structure of local current annealed amorphous ribbons

Abstract Positive and negative magnetostrictive amorphous ribbons have been locally current annealed under local stress to induce different anisotropies, which have been studied by observing the magnetic domains. In annealed samples under low applied stresses, the induced anisotropy is caused by the internal mechanical stresses produced during the thermal treatment due to the change in volume of the annealed zones. In annealed samples under high stresses, the main origin of the induced anisotropy is in the stresses produced by plastic deformation. After current annealing, local changes in the magnetostriction constant have been found in Co-based amorphous ribbons with low magnetostriction constant.

Current effects in magnetostrictive piezoelectric sensors

Some important improvements in magnetostrictive piezoelectric sensors have been obtained by applying an alternating current to the ferromagnetic amorphous ribbon. First, we present a way to minimize the hysteresis in these devices using a demagnetizing current through the magnetic sample. Second, the current, at a frequency half that of the longitudinal piezoelectric resonance, is used to induce size changes in the high-magnetostriction amorphous ribbon, and these changes, which depend on the external magnetic field, can be read by the piezoelectric support. Then, with this configuration, it is not necessary to have a coil for the detection of a magnetic field.

Magnetization processes in samples with modulated anisotropy

Abstract We have induced a helical anisotropy distribution by current annealing, in low-magnetostriction amorphous ribbons. In these samples the anisotropy direction rotates 180° continuously from one surface of the ribbon to the other. In this paper we report a theoretical and experimental study showing chirality conservation during the magnetization process in these samples. The chirality conservation implies that the sign of magnetization chirality must be the same as the anisotropy one. This restriction controls the magnetization processes producing large Barkhausen discontinuities.

Domain structure of laser annealed amorphous ribbons

Abstract The domain structure of amorphous ribbons with different magnetostriction constants has been studied after different laser annealing. The results can be explained assuming a change in the volume of the irradiated areas that produces a non-uniform stress distribution in the samples.

Influence of substrate geometry on the magnetic properties of CoP cylindrical multilayers

Abstract CoP multilayers have been electrodeposited on Cu wires. By applying external torsion, it is possible to induce helical anisotropies that become permanent when the torsion is removed. These anisotropies and consequently the magnetization process can be controlled by the magnitude of the torsion. The induced Matteucci effect makes the samples suitable as nuclei for magnetic sensors.

Micromagnetic structures in square magnetic nanodots

Abstract The structure of magnetization in magnetic square dots is studied in the range of tens of nanometer by means of micromagnetic simulations. Two magnetic configurations are found, diagonal and vortex structures for thin films, flower and vortex for magnetic nanocubes and a hybrid flower in bulk and vortex near the surfaces for dots with thicknesses larger than dot edge length.

Magnetic behavior of amorphous ribbons with induced helical anisotropy

Abstract Amorphous samples with helical induced anisotropy show magnetization processes that can be controlled by applying a longitudinal magnetic field simultaneously with an alternating current flowing through the sample. By varying the current amplitude and the phase difference between the current and the applied field, a wide range of coercivity and susceptibility values can be achieved.