C. Aroca

Transversal magnetic field effect on Fe40Ni40P14B6 amorphous alloys

Abstract A study about the influence of an electric current flowing through an amorphous ribbon Fe 40 Ni 40 P 14 B 6 has been done. It has been found that the magnetization curves are strongly influenced by such a current (from 0 up to 5000 Hz). Bitter patterns under the action of the current have been observed in order to gain a better knowledge of these effects. The wall energy has been evaluated from a simple model.

Magnetoelastic effects in amorphous Fe 40 Ni 40 P 14 B 6 alloys

The influence of compressive, tensile, and bending stresses on the magnetization processes, anisotropy energy, and remanence of an as-quenched amorphous Fe 40 Ni 40 P 14 B 6 ribbon has been studied. The magnetostriction constant has been obtained from the variation of the susceptibility with the applied compressive stress. To better understand the results, domain structures have been observed by using the Bitter technique. Our results show that the Metglas ribbon has a central region with compressive stress, while the edge regions have tensile stress. So, the influence of these regions on the magnetization processes will be very different according to the applied stress.

Magnetization processes and optimal performance of magnetostrictive piezoelectric sensors

We discuss the magnetization processes in sensors based on the superposition of a magneto‐ restrictive amorphous ribbon over a piezoelectric plate. These devices show an unusual behavior of the null condition in the response curves, which we have related theoretically and experimentally to the coercive force of the magnetic sample and to changes in the magnetic domain pattern for frequencies near the longitudinal piezoelectric resonance frequency.

Flux-gate sensor based on planar technology

A fluxgate-like magnetometer using planar technology has been developed. The performance is comparable to conventional fluxgates. Due to minor inductive and capacitive effects of the planar coils, higher exciting frequencies can be used. >

Measuring the exchange constant Aex in metglas 2826

Abstract We have measured the energy of Blochs walls in amorphous ferromagnetic ribbons using a method devised by R. Aleonard et al. for thin monocrystalline ferromagnetic films. To do this, we had to induce uni-directional anysotropy in the amorphous samples using stress. By measuring the movements of the walls for different current intensities, using the Bitter technique, we have obtained the wall energy value and thus the exchange constant A ex . Our results were of the order 6 × 10 −12 J/Mm which tallies with the results of other researchers who used different methods.

Matteucci effect as exhibited by cylindrical CoP amorphous multilayers

CoP amorphous samples, electrodeposited on copper wires and exhibiting a longitudinal magnetic anisotropy, show a spontaneous Matteucci effect once the substrate has been subjected to torque. This induces an easy axis to allow for magnetization to occur, breaking away from its original longitudinal direction. The magnetic domain structures, as observed by the Bitter technique, revealed that the anisotropy changes direction, rotating gradually from its initial longitudinal position to a 45° helix, as the torque was increased. The reversible part of the circular magnetization switching curves, set against the longitudinal magnetic field, was fitted by assuming a magnetization rotation model in which constant anisotropic magnitude values were hardly modified, while allowing changes in direction.

Magnetostatic energy calculations in two- and three-dimensional arrays of ferromagnetic prisms

Exact analytic expressions for magnetostatic energy calculations in arrays of ferromagnetic prisms are presented. They apply to two-dimensional (2-D) and three-dimensional (3-D) arrays of variable length prisms with uniform magnetization inside each prism. This permits the study of irregular magnetic structures allowing also a variable grid where the size of the cells depends on the structure itself. These expressions cover all possible cases for 2-D and 3-D problems.

Induction of bistability in low-magnetostriction amorphous ribbons

Abstract Bistability phenomena recently observed in amorphous wires can be explained by magnetoelastic coupling between two zones with different anisotropy. In this work we show the induction of bistability in amorphous ribbons with low magnetostriction (Metglas 2705M) using the exchange coupling in zones with a continuous varying anisotropy direction.

Study of magnetic domains in amorphous ribbons by scanning electron acoustic microscopy

Scanning electron acoustic microscopy (SEAM) has been used in the observation of domain walls in iron‐ and cobalt‐based amorphous alloys ribbons. Controlled magnetic annealing experiments enabled the direct identification of domain walls in SEAM micrographs. Walls in perpendicular anisotropy regions of the high magnetostriction samples show a particular high contrast, probably related to the wall stress field.

Study of the dynamic interaction of a domain wall with a pinning plane

The motion of a domain wall under the action of an alternating magnetic field was studied during its interaction with a pinning plane. First and second harmonics of the electronic force were measured by a lock-in amplifier, using a computer-controlled system. Good agreement was obtained between theory and experiment. Therefore, results of these experiments were used to determine the characteristics of the pinning place in the sample. The optimal frequency and amplitude of the exciting field have been investigated using this effect and have been used to develop a magnetic sensor. >