Amorphous Magnetic Core Research Articles

Carboxyl and negative charge-functionalized superparamagnetic nanochains with amorphous carbon shell and magnetic core: synthesis and their application in removal of heavy metal ions

This communication describes carboxyl-functionalized nanochains with amorphous carbon shell (18 nm) and magnetic core using ferrocene as a single reactant under the induction of an external magnetic field (0.40 T), which shows a superparamagnetic behavior and magnetization saturation of 38.6 emu g(-1). Because of mesoporous structure (3.8 nm) and surface negative charge (-35.18 mV), the nanochains can be used as adsorbent for removing the heavy metal ions (90%) from aqueous solution.

Novel Fe-based amorphous magnetic powder cores with ultra-low core losses

Amorphous magnetic alloy powders were prepared from bulk metallic glasses Fe74Cr2Mo2Sn2P10Si4B4C2 with supercooled liquid region of 32 K by water atomization. Amorphous magnetic powder core precursor was produced from a mixture of the amorphous alloy powder with addition of insulation and bonding materials by mold compacting at room temperature. After annealing the core precursor, the amorphous magnetic core exhibits superior magnetic properties as compared with molypermalloy powder core. The initial permeability up to 1 MHz was about 80, the flux density at 300 Oe was 1.06 T and the core loss at 100 kHz for Bm=0.1 T was only 329 kW/m3. The ultra-low core loss is attributed to the combination of relatively high resistivity and the amorphous structure of the Fe-based amorphous powder. Besides the outstanding magnetic properties, the Fe-based amorphous magnetic powder core had a much lower cost which renders the powder cores a potential candidate for a variety of industrial applications.

Some industrial applications of amorphous and nanocrystalline alloys

The example of successful realization of developments of Institute for Metal Physics of National Academy of Sciences of Ukraine in the field of nanotechnology is organization and successful, during 14 years, functioning of production of modern precision amorphous and nanocrystalline magnetic cores in the frames of the small research-and-production enterprise MELTA Ltd. The most important, from the practical standpoint, high heat-time stability of initial magnetic permeability of cores is provided by using new methods of final treatment of cores, minimization of their package influence on characteristics of the process using liquid impregnation heat-resistant materials and new polymeric coatings. The most effective fields of industrial use of MELTA® magnetic cores are ground leakage current sensors, current measuring transformers (converters), power medium frequency, broadband and pulse small-size transformers, filter chokes, reactors, storage transformers and ferroprobes.

A Micro Fluxgate Magnetic Sensor Using New Printed Circuit Board Technology

We have developed a micro fluxgate magnetic sensor using new printed circuit board (PCB) technology. The fluxgate sensor consisted of five PCB stack layers including one layer of magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core was made of micro patterned amorphous magnetic ribbon with an extremely high DC permeability of ~100,000, and the core had a rectangular ring shape. Four outer layers as an excitation and pickup coils had a planar solenoid structure. The amorphous magnetic core was easily saturated due to the high permeability, low coercive field, and closed magnetic path for the excitation field. The chip size of the fabricated sensing element was 7.3 × 5.7 mm2. Excellent linear response over the range of –100 μT to +100 μT was obtained with sensitivity of 780 V/T at excitation sine wave of 3 Vp-p and 360 kHz. A very low power consumption of ~8 mW was measured. This low power, small size, and high sensitive fluxgate sensor to measure a low magnetic field is very useful for various applications.

Microfluxgate sensor with amorphous cobalt (Co–Nb–Zr) soft magnetic core for electronic compass

A silicon based microfluxgate sensor with a cobalt based amorphous soft magnetic core for electronic compass is presented in this paper. A sputtered Co85Nb12Zr3 magnetic core having a rectangular ring shape is combined with microcopper solenoid coils for excitation and pickup, which were wound alternately around the core to increase the number of coil turns. The Co85Nb12Zr3 as a core material is adopted for improving properties of the magnetic core and easy integration with micromachining processes to achieve a small size of the sensor. The sputtered Co85Nb12Zr3 showed dc effective permeability of ∼10000 and an extremely low coercivity of ∼0.03Oe with the thickness of 1μm. The Co85Nb12Zr3 as a thin film core with high permeability and low coercivity was easily saturated by a low excitation magnetic field, enhancing the sensitivity and linearity of the microfluxgate sensor. Finally, the sensor showed excellent linearity response over the range of −300 to 300μT with sensitivity of 60V∕T at the excitation condition of 3.0Vp-p and 5.0 MHz square wave form. The sensor size excluding pad region is about 0.55×1.4mm2.

Embedded Micro-Flux-Gate Magnetic Sensor in Printed Circuit Board

We have developed a micro-flux-gate magnetic sensor using a new printed circuit board (PCB) technology. The flux-gate sensor consists of five PCB stack layers including one layer of magnetic core and four layers of excitation and pickup coils. The center layer as a magnetic core is made of a micropatterned amorphous magnetic ribbon with an extremely high DC permeability of ∼100,000; the core has a rectangular ring shape. The four outer layers as excitation and pickup coils have a planar solenoid structure. The amorphous magnetic core is easily saturated due to the low coercive field and closed magnetic path of the excitation field. The chip size of the fabricated sensing element is 9.8 ×5.7 mm2. Excellent linear response over the range of -100 to +100 µT is obtained with 1460 V/T sensitivity at an excitation sine wave of 3 Vp–p and 360 kHz. A low power consumption of ∼10 mW was measured.

Triaxial fluxgate gradiometer of high stability and linearity

A novel highly stable magnetic fluxgate vector gradiometer is presented in this paper. It is based on two triaxial fluxgate sensors with the Compact Spherical Coil (CSC) feedback to demonstrate the feasibility of such instrument (the full gradient instrument will consist of at least four triaxial sensors for measuring all the components of the gradient tensor). The sensors have been designed and constructed for the geopotential German satellite CHAMP, and are based on the instrument flying on the Danish satellite Ørsted dedicated to measure the Earth's magnetic field with very high precision. The transducers are of the ringcore type with very low noise and high thermal stability. They use amorphous metal magnetic core (Vitrovac 6025). The cores have been annealed in two different processes with different temperatures and stress. With this instrument, three components of the gradient tensor can be measured with a precision better than 100 pT rms/m. The noise of the gradiometer is 93 pT rms/m in the band 0.01–10 Hz (30.1 pT rms/(Hz 1/2 m) at 1 Hz).

Compact room-temperature induction magnetometer with superconducting quantum interference device level field sensitivity

In this article, we describe significant developments in the design and construction of robust and compact room-temperature induction magnetometers with magnetic field sensitivities comparable to those usually associated only with superconducting quantum interference device (SQUID) magnetometers operating at cryogenic temperatures. In this system, we make use of both temperature independent amorphous magnetic core materials and ultralow noise signal processing electronics to achieve a spot noise figure of 14 fT/Hz at 300 Hz measured in a specially constructed, very low field environment. We present results over an operating bandwidth of 30 mHz to 3 kHz and show that linearity is preserved over almost six decades in an applied magnetic field amplitude. We compare the spectral noise of our systems with recently published data on SQUID magnetometers.

PCB 기판에 내장된 마이크로 플럭스게이트 센서

This paper presents a micro fluxgate sensor in printed circuit board (PCB). The fluxgate sensor consists of five PCB stack layers including one layer magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core is made of a micro patterned amorphous magnetic ribbon and the core has a rectangular-ring shape. The amorphous magnetic core is easily saturated due to the low coercive field and closed magnetic path for the excitation field. Four outer layers as an excitation and pick-up coils have a planar solenoid structure. The chip size of the fabricated sensing element is 7.3<TEX>$\times$</TEX>5.7<TEX>$\textrm{mm}^2$</TEX>. Excellent linear response over the range of -100<TEX>$\mu$</TEX>T to +100<TEX>$\mu$</TEX>T is obtained with 540V/T sensitivity at excitation square wave of 3 <TEX>$V_{p-p}$</TEX> and 360kHz. The very low power consumption of ~8mW was measured. This magnetic sensing element, which measures the lower fields than 50<TEX>$\mu$</TEX>T, is very useful for various applications such as: portable navigation systems, military research, medical research, and space research.h.

Power Loss and Relative Permeability of Annealed Amorphous Magnetic Cores for Electrical Machines

The power loss and relative permeability of two amorphous magnetic cores are investigated. The cores employ two different amorphous alloy samples. This investigation is carried out in as-cast and annealed states at specified range of frequencies under sinusoidal flux conditions.

An effect of manufacturing conditions on the properties of a 250 kVA three-limb three-phase distribution amorphous transformer

The research results for different stages of production of a three-phase 250 kVA distribution transformer using three-limb amorphous magnetic core have been presented. The core is made from six frames wound from 23 μm thick Metglas 2605 TCA ribbon. Magnetic characteristics for the frames and three-limb core were measured. The 250 kVA distribution transformer was manufactured.

Printed circuit board integrated fluxgate sensor

We have developed a cheap and simple trilayer printed circuit board (PCB)-based technology, adapted for the fabrication of fluxgate magnetic sensors. The two outer layers of the PCB stack comprise the electrical windings of the fluxgate, while the inner layer is made of patterned amorphous magnetic core with extremely high relative magnetic permeability ( μ r≈100,000). The output voltage and the sensitivity of the fluxgate devices have been studied as a function of the external field and of the geometry of the magnetic core. We have found a relatively high sensitivity of 18 V/T at an excitation current frequency of 10 kHz. The results obtained clearly show the potential of this miniaturised fluxgate device for application as a magnetic field sensor.

Functional study of fluxgate sensors with amorphous magnetic materials cores

A functional study of the TFS-3 type fluxgate sensor with amorphous magnetic material cores is made. The magnetic material used in these sensors is Romanian amorphous material Co68.25Fe4.5Si12.25B15 thin ribbon produced at the Institute of Technical Physics, Iasi and prepared by rapid quenching from the melt on a rotating copper wheel. The sensor's functional parameters and thermostability were measured. The sensor sensitivity is between 4.5 and 5.5 μV nt−1 and for fields greater than 100 nT does not depend on temperature variation in the range +20 to +70°C. Also the temperature variation does not influence the noise of the sensor which does not exceed 600 pTpp. The offset thermostability corresponds to a thermal drift of 1 nT °C−1 over the whole mentioned temperature range. The ability of sensors to measure a.c. magnetic fields by means of the two side bands of the second harmonic was studied using Fourier analysis. The study was done for a.c. field frequencies of up to 15 kHz, at excitation frequencies up to 30 kHz. For an induction field up to 26 μTpp the response is linear, showing the possibility of using the sensor for also measuring low frequency a.c. fields.

Magnet-Displacement Sensor Using Magneto-Inductive Elements for Sensing Eyelid Movement

We previously constructed an accurate displacement sensor for detection of eyelid movement, using an amorphous magnetic core multivibrator. Improvements in eyelid motion sensors are necessary to achieve independence of the magnetization direction of the cores as well as a broadened visual field. We constructed a second displacement sensor for detection of eyelid movement, this time using amorphous wire magneto-inductive (MI) elements. The elements were formed from tension-annealed zero-magnetostriction amorphous wires. The MI effect and the symmetrical MI characteristics of the elements were used to form thin sensor heads without coils. Inductances change independently of the magnet magnetization directions.

Development of a beam current monitor by using an amorphous magnetic core

The high performance amorphous magnetic core monitor (ACM) for the measurement of electron beam currents has been developed. This monitor is composed of an amorphous magnetic core, radiation shields, a winding, magnetic absorbers, a ceramic vacuum duct and a SMA connector. The ACM showed the very fast rise and fall times ( < 1 ns), the high sensitivity (5 V/A at 50 Ω load), the good linearity, and good S/N ratio due to the high permeability of the amorphous magnetic core. The monitor works as a primary transformer. The time-response was simulated by an electric circuit analysis code.

磁気インダクタンス素子による眼けん運動検出用磁石変位センサ

We previously constructed an accurate magnetdisplacement sensor for detection of eyelid movement, using an amorphous magnetic core multivibrator. However, some improvements in the eyelid movement sensor are necessary in order to achieve independence of the magnetization direction of the cores and a wider sight space. We therefore constructed another accurate magnet-displacement sensor for detection of eyelid movement, this time, using amorphous wire magnetoinductive (or MI) elements. The elements were formed by using tension annealed zeromagnetostrictive amorphous wires. The MI effect and the symmetrical MI characteristics of the elements are used to form thinner sensor heads having no coils and to change their inductances independent of the magnetization directions.

Tablet Using Matteucci Effect of Amorphous Magnetic Wires

This article describes a new tablet for inputting handwritten characters to computers using amorphous magnetic wires employing the Matteucci effect, which is sensitive to perpendicular ac magnetic fields. The Matteucci voltage e M with a double-frequency-pulse shaped ac voltage is induced across the ends of an amorphous wire when an arbitrary point is vertically magnetized by a pen-shaped coil with an amorphous magnetic core. The value of e M was nearly constant as the pen was slid along the wire, but rapidly decreased with pen displacement vertical to the wire. An amorphous wire matrix was constructed, with each of the ten wires in the X and Y directions spaced at 5 mm intervals, and with Matteucci voltage pulses converted to dc voltages through peak-holders. Handwritten characters are displayed on a microcomputer display using a multiplexer, A/D converter, and position detection software.

Long-Term Aging Effect on Coercive Force in Amorphous Magnetic Cores and Estimation of Its Deterioration at Operating Temperature

The long-term aging effect on the coercive force was studied for Co-based and Fe-based amorphous cores. Both amorphous cores show the same tendency in the aging process of their coercivities; they increase linearly with the logarithm of aging time over one year. The nonsaturated aging kinetics of the coercive force were analyzed by a method based on the pair ordering model reported by Taniguchi. The method does not need the saturation value of the coercive force and enables us to estimate the deterioration of the cores at operating temperatures which are lower than the aging temperatures. The increase in the coercivity for our cores was estimated to be less than 15 mOe after 106 h at 100°C.

Power loss measurements in amorphous soft magnetic cores

A highly automatized measuring system was developed to determine the power loss in amorphous soft magnetic cores even at high frequency and near saturation induction. The power loss was investigated on custom made ribbons as a function of composition, processing conditions and heat treatment as well as the exciting frequency and induction.

The economics of amorphous core power transformers for induction heating applications at 20–50 kHz

The advantages of the use of amorphous magnetic cores in power transformers for induction heating applications in the frequency range 20–50 kHz are discussed. These advantages are pointed out presenting the characteristics and costs at different frequencies of a shell-type pancake coils power unit.