Spiral Annealing of Magnetic Microwires.

A preprocessing technique named "spiral annealing" was applied for the first time to magnetic microwires. In this process, the sample was arranged in a flat spiral shape during annealing, and subsequent measurements were conducted on the unbent sample with the induced stress distribution along and transverse to the sample. The research utilized both magnetic and magneto-optical methods.

Dependence of Magnetic Properties of As-Prepared Nanocrystalline NiMnGa Glass-Coated Microwires on the Geometrical Aspect Ratio.

We have prepared NiMnGa glass-coated microwires with different geometrical aspect ratios, = / (-diameter of metallic nucleus, and -total diameter). The structure and magnetic properties are investigated in a wide range of temperatures and magnetic fields. The XRD analysis illustrates stable microstructure in the range of from 0.

Comparison of the Magnetic and Structural Properties of MnFePSi Microwires and MnFePSi Bulk Alloy.

We provide comparative studies of the structural, morphological, microstructural, and magnetic properties of MnFePSi-glass-coated microwires (MnFePSi-GCMWs) and bulk MnFePSi at different temperatures and magnetic fields. The structure of MnFePSi GCMWs prepared by the Taylor-Ulitovsky method consists of the main FeP phase and secondary impurities phases of MnSi and FeSi, as confirmed by XRD analysis. Additionally, a notable reduction in the average grain size from 24 µm for the bulk sample to 36 nm for the glass-coated microwire sample is observed.

Monitoring the Velocity of Domain Wall Motion in Magnetic Microwires.

An approach was proposed to control the displacement of domain walls in magnetic microwires, which are employed in magnetic sensors. The velocity of the domain wall can be altered by the interaction of two magnetic microwires of distinct types. Thorough investigations were conducted utilizing fluxmetric, Sixtus-Tonks, and magneto-optical techniques.

Anomalous Magnetic Anisotropy Behaviour in Co-Rich and Fe-Rich Glass-Coated Microwires under Applied Stress.

In this article, we study the effect of annealing temperature and applied stress on the magnetic properties of Fe71.80B13.27Si11.

Optimization of Magnetoimpedance Effect and Magnetic Properties of Fe-Rich Glass-Coated Microwires by Annealing.

As-prepared Fe-rich microwires with perfectly rectangular hysteresis loops present magnetization reversal through fast domain wall propagation, while the giant magnetoimpedance (GMI) effect in Fe-rich microwires is rather low. However, the lower cost of Fe-rich microwires makes them attractive for magnetic sensors applications. We studied the effect of conventional (furnace) annealing and Joule heating on magnetic-propertied domain wall (DW) dynamics and the GMI effect in two Fe microwires with different geometries.

Carbon-Doped CoMnSi Heusler Alloy Microwires with Improved Thermal Characteristics of Magnetization for Multifunctional Applications.

In the current work, we illustrate the effect of adding a small amount of carbon to very common CoMnSi Heusler alloy-based glass-coated microwires. A significant change in the magnetic and structure structural properties was observed for the new alloy CoMnSiC compared to the CoMnSi alloy. Magneto-structural investigations were performed to clarify the main physical parameters, i.

Enhancing the Squareness and Bi-Phase Magnetic Switching of CoFeSi Microwires for Sensing Application.

In the current study we have obtained CoFeSi glass-coated microwires with different geometrical aspect ratios, = d/D (diameter of metallic nucleus, d and total diameter, D). The structure and magnetic properties are investigated at a wide range of temperatures. XRD analysis illustrates a notable change in the microstructure by increasing the aspect ratio of CoFeSi-glass-coated microwires.

Determination of Magnetic Structures in Magnetic Microwires with Longitudinally Distributed Magnetic Anisotropy.

We studied the magnetic properties of a glass-covered amorphous microwire that was stress-annealed at temperatures distributed along the microwire length. The Sixtus-Tonks, Kerr effect microscopy and magnetic impedance techniques have been applied. There was a transformation of the magnetic structure across the zones subjected to annealing at different temperatures.

Tuning of Magnetoimpedance Effect and Magnetic Properties of Fe-Rich Glass-Coated Microwires by Joule Heating.

The influence of Joule heating on magnetic properties, giant magnetoimpedance (GMI) effect and domain wall (DW) dynamics of FeBSiC glass-coated microwires was studied. A remarkable (up to an order of magnitude) increase in GMI ratio is observed in Joule heated samples in the frequency range from 10 MHz to 1 GHz. In particular, an increase in GMI ratio, from 10% up to 140% at 200 MHz is observed in Joule heated samples.

Development of Co-Rich Microwires with Graded Magnetic Anisotropy.

In this paper, a gradual change in the hysteresis loop of Co-rich glass-coated microwire stress-annealed at variable temperature is observed. Such microwires annealed with a temperature gradient also present a variable squareness ratio and magnetic anisotropy field along the microwire's length. The obtained graded anisotropy has been attributed to a gradual modification of the domain structure along the microwire originated by a counterbalance between shape, magnetoelastic, and induced magnetic anisotropies.

Magneto-Transport Properties of Co-Cu Thin Films Obtained by Co-Sputtering and Sputter Gas Aggregation.

CuCo thin films have been obtained by sputtering (x = 3, 9) and sputter gas aggregation (x = 2.5, 7.5) and subsequent annealing at 400 °C for 1 h.

Magnetic Microwires with Unique Combination of Magnetic Properties Suitable for Various Magnetic Sensor Applications.

There is a pressing demand to improve the performance of cost-effective soft magnetic materials for use in high performance sensors and devices. Giant Magneto-impedance effect (GMI), or fast single domain wall (DW) propagation can be observed in properly processed magnetic microwires. In this paper we have identified the routes to obtain microwires with unique combination of magnetic properties allowing observation of fast and single DW propagation and GMI effect in the same microwire.

Reversible and Non-Reversible Transformation of Magnetic Structure in Amorphous Microwires.

We provide an overview of the tools directed to reversible and irreversible transformations of the magnetic structure of glass-covered microwires. The irreversible tools are the selection of the chemical composition, geometric ratio, and the stress-annealing. For reversible tuning we use the combination of magnetic fields and mechanical stresses.

Magnetoimpedance Response and Field Sensitivity in Stress-Annealed Co-Based Microwires for Sensor Applications.

Amorphous soft magnetic microwires have attracted much attention in the area of sensor applications due to their excellent properties. In this work, we study the influence of annealing treatments (stress and conventional) in the giant magnetoimpedance (GMI) response and the field sensitivity of the soft magnetic CoFeNiBSiMoC glass-coated microwires. Here we report a remarkable and simultaneous enhancement of GMI effect and field sensitivity.

Optimization of magnetic properties and GMI effect of Thin Co-rich Microwires for GMI Microsensors.

Magnetic microwires can present excellent soft magnetic properties and a giant magnetoimpedance effect. In this paper, we present our last results on the effect of postprocessing allowing optimization of the magnetoimpedance effect in Co-rich microwires suitable for magnetic microsensor applications. Giant magnetoimpedance effect improvement was achieved either by annealing or stress-annealing.

Soft Magnetic Amorphous Microwires for Stress and Temperature Sensory Applications.

Amorphous ferromagnetic materials in the form of microwires are of interest for the development of various sensors. This paper analyzes and argues for the use of microwires of two basic compositions of CoFeBSiCr and FeCoBSiCrMo as stress/strain and temperature sensors, respectively. The following properties make them suitable for innovative applications: miniature dimensions, small coercivity, low anisotropy and magnetostriction, tunable magnetic structure, magnetic anisotropy, and Curie temperature by annealing.

Development of Magnetic Microwires for Magnetic Sensor Applications.

Thin magnetic wires can present excellent soft magnetic properties (with coercivities up to 4 A/m), Giant Magneto-impedance effect, GMI, or rectangular hysteresis loops combined with quite fast domain wall, DW, propagation. In this paper we overview the magnetic properties of thin magnetic wires and post-processing allowing optimization of their magnetic properties for magnetic sensor applications. We concluded that the GMI effect, magnetic softness or DW dynamics of microwires can be tailored by controlling the magnetoelastic anisotropy of as-prepared microwires or controlling their internal stresses and domain structure by appropriate thermal treatment.

Impact of Stress Annealing on the Magnetization Process of Amorphous and Nanocrystalline Co-Based Microwires.

The domain wall (DW) dynamics of amorphous and nanocrystalline Co-based glass-coated microwires are explored under the influence of stress annealing. Different annealing profiles have enabled remarkable changes in coercivity and magnetostriction values of Co-based amorphous microwires with initially negative magnitude, allowing induced magnetic bistability in stress-annealed samples and, consequently, high DW velocity has been observed. Similarly, Co-based nanocrystalline microwires with positive magnetostriction and spontaneous bistability have featured high DW velocity.

Magnetic Characterization in the Rayleigh Region of Nanocrystalline Magnetic Cores.

We report on the structural and magnetic characterization of two nanocrystalline Finemet-type magnetic cores. The nanocrystalline structure developed after annealing the amorphous precursor alloy at 550 °C for 30 and 60 min of annealing time. Structural analysis carried out by means of X-ray diffraction providing useful information on the grain size mean and partial volume of the nanocrystalline phase.

Phase transitions, magnetotransport and magnetocaloric effects in a new family of quaternary Ni-Mn-In-Z Heusler alloys.

The magnetic, magnetotransport, and magnetocaloric properties near compound phase transitions in Ni50Mn35In14Z (Z = In, Ge, Al), and Ni48Co2Mn35In15 Heusler alloys have been studied using VSM and SQUID magnetometers (at magnetic fields (H) up to 5 T), four-probe method (at H = 0.005-1.5 T), and an adiabatic magnetocalorimeter (for H changes up to deltaH = 1.

Manipulation of domain wall dynamics in amorphous microwires through the magnetoelastic anisotropy.

We studied the effect of magnetoelastic anisotropy on domain wall (DW) dynamics and remagnetization process of magnetically bistable Fe-Co-rich microwires with metallic nucleus diameters (from 1.4 to 22 μm). We manipulated the magnetoelastic anisotropy applying the tensile stresses and changing the magnetostriction constant and strength of the internal stresses.

Thin magnetically soft wires for magnetic microsensors.

Recent advances in technology involving magnetic materials require development of novel advanced magnetic materials with improved magnetic and magneto-transport properties and with reduced dimensionality. Therefore magnetic materials with outstanding magnetic characteristics and reduced dimensionality have recently gained much attention. Among these magnetic materials a family of thin wires with reduced geometrical dimensions (of order of 1-30 μm in diameter) have gained importance within the last few years.