Fabrication and magnetic properties of hard/soft magnetostatically coupled FePt/FeNi multilayer microwires

3 pages, 5 figures.-- PACS: 75.70.Cn; 75.60.Ej; 75.50.Ww; 81.15.Pq; 68.65.Ac; 81.40.EfA family of multilayer microwires with hard/soft biphase magnetic behavior is here introduced. The microwires consist of a Fe63Pt27Si10 hard magnetic nucleus and a Fe20Ni80 soft outer shell separated by an intermediate insulating Pyrex glass microtube. The precursor FePtSi glass-coated microwire is fabricated by quenching and drawing technique, and its L10 hard magnetic phase is grown by postannealing treatment technique. The polycrystalline FeNi soft magnetic outer shell has been deposited by electroplating. The analysis of the low-field hysteresis loops of the FeNi soft phase after premagnetizing until near magnetic saturation provides information about the magnetostatic coupling between phases. The FeNi magnetization curve is shifted toward positive field when the FePt remanent magnetization is positive and vice versa. A systematic analysis of the magnetostatic coupling and the corresponding bias field arising from uncompensated poles of the premagnetized FePt hard phase has been performed. The strength of the bias field is shown to increase with the reduction of thickness of the FeNi layer. These magnetostatically coupled biphase systems are thought to be of large potential interest as sensing elements in sensor devices.The work has been developed under the Project No. MAT2004-00150 supported by the Spanish Ministry of Education and Science, MEC. J. T. acknowledges a FPU program fellowship from MEC.Peer reviewe

Growth modes of nanoparticle superlattice thin films

We report about the fabrication and characterization of iron oxide nanoparticle thin film superlattices. The formation into different film morphologies is controlled by tuning the particle plus solvent-to-substrate interaction. It turns out that the wetting vs. dewetting properties of the solvent before the self-assembly process during solvent evaporation plays a major role to determine the resulting film morphology. In addition to layerwise growth also three-dimensional mesocrystalline growth is evidenced. The understanding of the mechanisms ruling nanoparticle self-assembly represents an important step toward the fabrication of novel materials with tailored optical, magnetic or electrical transport properties

Fabrication and magnetic properties of hard/soft magnetostatically coupled FePt/FeNi multilayer microwires

3 pages, 5 figures.-- PACS: 75.70.Cn; 75.60.Ej; 75.50.Ww; 81.15.Pq; 68.65.Ac; 81.40.EfA family of multilayer microwires with hard/soft biphase magnetic behavior is here introduced. The microwires consist of a Fe63Pt27Si10 hard magnetic nucleus and a Fe20Ni80 soft outer shell separated by an intermediate insulating Pyrex glass microtube. The precursor FePtSi glass-coated microwire is fabricated by quenching and drawing technique, and its L10 hard magnetic phase is grown by postannealing treatment technique. The polycrystalline FeNi soft magnetic outer shell has been deposited by electroplating. The analysis of the low-field hysteresis loops of the FeNi soft phase after premagnetizing until near magnetic saturation provides information about the magnetostatic coupling between phases. The FeNi magnetization curve is shifted toward positive field when the FePt remanent magnetization is positive and vice versa. A systematic analysis of the magnetostatic coupling and the corresponding bias field arising from uncompensated poles of the premagnetized FePt hard phase has been performed. The strength of the bias field is shown to increase with the reduction of thickness of the FeNi layer. These magnetostatically coupled biphase systems are thought to be of large potential interest as sensing elements in sensor devices.The work has been developed under the Project No. MAT2004-00150 supported by the Spanish Ministry of Education and Science, MEC. J. T. acknowledges a FPU program fellowship from MEC.Peer reviewe

Locally induced domain wall damping in a thin magnetic wire

The damping mechanisms affecting the motion of a single domain wall were studied in a thin bistable magnetic wire. It was found that the overall damping is frequency and temperature dependent through the locally induced anisotropy via structural relaxation. This phenomenon can increase the overall damping by one order of magnitude and enables an effective tailoring of the domain wall dynamics according to required application.Peer reviewe

Hilos magnéticos bimetálicos con anisotropía helicoidal, proceso de fabricación y aplicaciones

Hilos magnéticos bimetálicos con anisotropía helicoidal, proceso de fabricación y aplicaciones. La presente invención se refiere un hilo magnético bimetálico que comprende cuatro capas diferentes, siendo una de ellas una capa ferromagnética con anisotropía helicoidal. Por tanto, la invención se encuentra enmarcada dentro del campo de materiales magnéticos, y concretamente de hilos magnéticos multicapas, y su aplicación dentro del campo de los elementos sensores, en particular el de los sensores magnéticos.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad Técnica ChecaA1 Solicitud de patentes con informe sobre el estado de la técnic

Double large Barkhausen jump in soft/soft composite microwires

The magnetic properties of double layer microwires consisting of a soft FeSiBP amorphous core, an intermediate non-magnetic glass spacer and a softer FeNi outer shell have been investigated. As in the case of other magnetostatically coupled two-phase systems, the hysteresis loops are characterized by two well-defined Barkhausen jumps corresponding each to the magnetization reversal of the individual phases, separated by a plateau. The strong dipolar interaction that leads to the appearance of the plateau is investigated in terms of the microwire geometry. It is shown that this source of coupling is capable of increasing up to one order of magnitude the switching field of the Fe-rich core. Thus, magnetic bistability can be effectively controlled in these kinds of composite wires.Peer reviewe

Nonlinear magnetoimpedance and parametric excitation of standing spin waves in a glass-covered microwire

3 pages, 3 figures.-- PACS: 75.47.De; 75.30.DsThe giant magnetoimpedance of an 8.5 µm glass-covered amorphous microwire was investigated in the frequency range of 10 MHz–3.5 GHz. It was found that when the exciting microwave current exceeds some threshold value, a periodic fine structure appears in the frequency dependence of the complex impedance. The appearance of this nonlinear phenomenon is interpreted to be a consequence of the parametric excitation of standing spin waves.This work was done in the frame of common project AS CR–CSIC “Amorphous and nanocrystalline soft magnetic heterostructures and their applications” and was partly supported by the Grant Agency of the Czech Republic (Grant No. 102/08/0743) and Academy of Sciences of the Czech Republic (Grant No. AVOZ 10100520), as well as by the Project No. MAT2007-65420-C02-01 supported by the Spanish Ministry of Science and Innovation.Peer reviewe

M-H loop tracer based on digital signal processing for low frequency characterization of extremely thin magnetic wires

4 pages, 4 figures.A high-sensitivity ac hysteresis loop tracer has been developed to measure the low frequency hysteresis loop of soft magnetic materials. It has been applied successfully to characterize straight pieces of amorphous glass-covered microwires with metallic nucleus down to 1.5 µm thick. Based on the electromagnetic induction law, the proposed design is extremely simple and exploits the capabilities of commercially available data acquisition cards together with digital signal processing in order to achieve high-sensitivity without the need of expensive analog equipment.This work was supported by the Spanish Ministry of Science and Innovation (MICINN) Project No. MAT2007-65420-C02-01, as well as by the research Program No. MSM6840770015 “Research of Methods and Systems for Measurement of Physical Quantities and Measured Data Processing” of the CTU in Prague sponsored by the Ministry of Education, Youth and Sports of the Czech Republic. G.I. acknowledges Spanish MICINN FPU fellowships program.Peer reviewe

Stress dependence of the switching field in glass-coated microwires with positive magnetostriction

We have studied the stress dependence of the switching field in the glass-coated FeNbSiB microwire. The stress dependence can be tailored by properly choosing the frequency of exciting magnetic field. At low frequencies, the switching field is weakly dependent on the mechanical stress, which is ideal for sensors of magnetic field or temperature. Increasing the frequency leads to the increase of the stress dependence of the switching field. The slope of the stress dependence is almost linear and the switching field increases its value from 128 A/m at 0 MPa to 242 A/m at 160 MPa. © 2012 Elsevier B.V. All rights reserved.Support by the project NanoCEXmat No. ITMS 26220120019, Slovak Grant APVV-0266-10, APVV-0027-11 and VEGA Grant no. 1/0076/09 is acknowledged.Peer Reviewe