Amorphous Ferromagnetic Materials Research Articles

Magnetoelectric Effect in Amorphous Ferromagnetic FeCoSiB/Langatate Monolithic Heterostructure for Magnetic Field Sensing.

This paper investigates the possibilities of creating magnetic field sensors using the direct magnetoelectric (ME) effect in a monolithic heterostructure of amorphous ferromagnetic material/langatate. Layers of 1.5 μm-thick FeCoSiB amorphous ferromagnetic material were deposited on the surface of the langatate single crystal using magnetron sputtering. At the resonance frequency of the structure, 107 kHz, the ME coefficient of linear conversion of 76.6 V/(Oe∙cm) was obtained. Furthermore, the nonlinear ME effect of voltage harmonic generation was observed with an increasing excitation magnetic field. The efficiency of generating the second and third harmonics was about 6.3 V/(Oe2∙cm) and 1.8 V/(Oe3∙cm), respectively. A hysteresis dependence of ME voltage on a permanent magnetic field was observed due to the presence of α-Fe iron crystalline phases in the magnetic layer. At the resonance frequency, the monolithic heterostructure had a sensitivity to the AC magnetic field of 4.6 V/Oe, a minimum detectable magnetic field of ~70 pT, and a low level of magnetic noise of 0.36 pT/Hz1/2, which allows it to be used in ME magnetic field sensors.

Microscope Stand for the Measurement and Characterization of Amorphous Ferromagnetic Materials

In this research, a microscope stand has been built which enables both the measurement of properties and the characterization of amorphous magnetic materials when they are subjected to an electric current. It is currently not possible to ascertain the real temperature during current annealing using a thermocouple, due to the thermal inertia and the fact that its mass is comparable to that of the amorphous material. To solve this, the infrared radiation of the material can be measured during the heating process by means of a microscope. In order to achieve this, it is necessary to place the material under the microscope so that the said radiation value may be obtained whilst avoiding buckling. The stand fulfills this function since it features a sliding part connected to a weight, which enables the measurement of the magnetic properties and the temperature of the amorphous ferromagnetic material using the microscope. The device developed is very useful for detecting crystallization processes in situ and it could also be used to study the growth of monocrystals and the recrystallization of grains.

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 Co71Fe5B11Si10Cr3 and Fe3.9(4.9)Co64.82B10.2Si12Cr9(8)Mo0.08 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. For example, these sensors can be used for testing the internal stress/strain condition of polymer composite materials and controlling the temperature of hypothermia treatments. The sensing operation is based on the two fundamental effects: the generation of higher frequency harmonics of the voltage pulse induced during remagnetization in wires demonstrating magnetic bistability, and magnetoimpedance.

Compositional variation of amorphous phase controlled coercivity of Nd60Fe30Al10 alloy

Abstract The coercivity of Nd-Fe-Al amorphous ferromagnetic materials originates from the combination of magnetic interaction and strong pinning of domain walls. Using Nd60Fe30Al10 alloys made under three cooling rates, we discovered an important microstructure parameter that can be used to strengthen interaction and pinning. By tuning the variations of composition difference between Nd-rich and Fe-rich amorphous regions, we enhanced the magnetic interaction and increased maximum restoring force per pin of Nd nanocrystals (with size

Magnetic Sensors Based on Amorphous Ferromagnetic Materials: A Review

Currently there are many types of sensors that are used in lots of applications. Among these, magnetic sensors are a good alternative for the detection and measurement of different phenomena because they are a “simple” and readily available technology. For the construction of such devices there are many magnetic materials available, although amorphous ferromagnetic materials are the most suitable. The existence in the market of these materials allows the production of different kinds of sensors, without requiring expensive manufacture investments for the magnetic cores. Furthermore, these are not fragile materials that require special care, favouring the construction of solid and reliable devices. Another important feature is that these sensors can be developed without electric contact between the measuring device and the sensor, making them especially fit for use in harsh environments. In this review we will look at the main types of developed magnetic sensors. This work presents the state of the art of magnetic sensors based on amorphous ferromagnetic materials used in modern technology: security devices, weapon detection, magnetic maps, car industry, credit cards, etc.

Soft magnetic properties and giant magnetoimpedance effect in thermally annealed amorphous Co68Fe4Cr3Si15B10 alloy ribbons

Giant magnetoimpedance (GMI) effect in amorphous soft magnetic materials has been intensively investigated owing to its promising technological applications. The GMI effect can be improved when an amorphous ferromagnetic material is subjected to proper heat treatments. In present work, in order to further improve the GMI effect in amorphous Co68Fe4Cr3Si15B10 ribbons, thermal annealing is employed to optimize the GMI effect of amorphous Co68Fe4Cr3Si15B10 ribbons. Magnetic measurements show that the soft magnetic properties of ribbons were affected significantly by thermal annealing. The saturation flux density of ribbons increases with increasing annealing temperature. Optimized annealing temperature of about 400°C gives lowest coercivity, highest permeability and electric conductivity. The frequency dependence of GMI effect in annealed Co68Fe4Cr3Si15B10 ribbons is discussed in details. The maximum GMI value of about 220% and sensitivity of about 106%/Oe were achieved at the driven frequency of 3MHz in the ribbon annealed at 400°C. It is clear that the enhanced maximum GMI ratio and sensitivity for the sample annealed is caused by its increased saturated flux density, permeability, electrical conductivity and reduced coercivity.

Magnetic properties measurement and discussion of an amorphous power transformer core at room and liquid nitrogen temperature

In energy generation, transmission and distribution systems, power transformers are one of the most common and important components. Consequently, the performance of these transformers is crucial to global efficiency of the systems. To optimize transformers efficiency, the selection of an adequate ferromagnetic material is very important. For example, the use of amorphous ferromagnetic materials in transformer cores, replacing crystalline electrical steels, decreases total magnetic losses of the device. Other possible solution to increase energy systems efficiency, is the installation of high temperature superconducting power transformers (HTS transformers), normally cooled by liquid nitrogen at 77 K. In order to contribute to HTS transformer efficiency improvement, a 562.5 VA transformer with an amorphous ferromagnetic core was designed and built. For this core, the most important magnetic properties are measured at room and cryogenic temperature, and then compared with those of a typical crystalline grain-oriented electrical steel. Amorphous material magnetic losses (static and dynamic) at room and 77K are also presented and discussed.

비정질 강자성체 CoSiB/Pd 다층박막의 두께에 따른 수직자기이방성 변화

Perpendicular magnetic anisotropy (PMA) is the phenomenon of magnetic thin film which is preferentially magnetized in a direction perpendicular to the film`s plane. Amorphous multilayer with PMA has been studied as the good candidate to realization of high density STT-MRAM (Spin Transfer Torque-Magnetic Random Access Memory). The current issue of high density STT-MRAM is a decrease in the switching current of the device and an application of amorphous materials which are most suitable devices. The amorphous ferromagnetic material has low saturated magnetization, low coercivity and high thermal stability. In this study, we presented amorphous ferromagnetic multilayer that consists of an amorphous alloy CoSiB and a nonmagnetic material Pd. We investigated the change of PMA of the multilayer (

Amorphous ferromagnetic CoSiB/Pd multilayer with perpendicular magnetic anisotropy

Perpendicular magnetic anisotropy has been studied for possible use in high-density spin transfer torque magnetic random access memories. The key issues of high-density spin transfer torque magnetic random access memories are decreasing the switching current and have the high thermal stability. In order to solve these problems, the approach of developing a new amorphous ferromagnetic material for use as a pinned layer for a multilayer with a low saturated magnetization value has been suggested. In a previous study, amorphous ferromagnetic material CoSiB was shown to have a low saturated magnetization (Ms = 470 emu/cm3) and a modest anisotropy constant (Ku = 1,500 erg/cm3). Then, we investigated the perpendicular magnetic anisotropy of a [CoSiB tCoSiB nm/Pt 1.4 nm]5 multilayer, where tCoSiB are 0.1, 0.2, 0.3, 0.4, and 0.5 nm. In this study, we present a new multilayer type based on the previous study, and this multilayer, CoSiB/Pd multilayer has the perpendicular magnetic anisotropy. In this letter, we have investigated the perpendicular magnetic anisotropies of a [CoSiB tCoSiB nm/Pd 1.3 nm]5 multilayer, where tCoSiB are 0.1, 0.2, 0.3, 0.4, 0.5, and 0.6 nm and [CoSiB 6.3 nm/Pd tPd nm]5 multilayer, where tPd are 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6 nm.

Perpendicular magnetic anisotropy in CoSiB/Pd multilayers with various thicknesses

In this letter, we report the perpendicular magnetic anisotropy of [CoSiB tCoSiB nm/Pd 1.3 nm]5 multilayer for tCoSiB equal to 0.1, 0.2, 0.3, 0.4, 0.5 and 0.6 nm and of [CoSiB 0.3 nm/Pd tPd nm]5 multilayer for tPd equal to 1.1, 1.2, 1.3, 1.4, 1.5, and 1.6 nm. We also presented to for [CoSiB 0.3 nm/Pd 1.3 nm]n multilayer for n equal to 3, 5, 7, 9, 11 and 13. The coercivity (Hc) and the saturation magnetization (Ms) of the amorphous ferromagnetic material Co75Si15B10 were taken to be 1.6 Oe and 407 emu/cm3, respectively. The Hc in [CoSiB tCoSiB nm/Pd 1.3 nm]5 multilayers increased with increasing tCoSiB to reach a maximum at tCoSiB = 0.3 nm and then decreased for tCoSiB > 0.3 nm. The highest Hc of 0.26 k Oe was obtained in [CoSiB 0.3 nm/Pd 1.3 nm]5 whereas the lowest Ms of 0.26 emu/cm3 was obtained in the [CoSiB 0.3 nm/Pd 1.3 nm]3 multilayer. Additional Pd layers did not contribute to the perpendicular magnetic anisotropy. The single-domain structure evolved into a striped multi-domain structure as the bilayer repetition number n was increased above 7 after which (n > 7) the hysteresis had a bow-tie shapes.

Perpendicular magnetic anisotropy of amorphous ferromagnetic CoSiB/[Pt,Au] multilayer

Perpendicular magnetic anisotropy is being widely studied as a possible candidate for a high-density spin-transfer torque magnetic random access memory. The key issues of a high-density spin-transfer torque magnetic random access memory are decreasing the switching current and the high thermal stability. In order to solve these problems, two approaches are suggested: One is the development a new amorphous ferromagnetic material as a pinned layer for a multilayer with a low saturated magnetization (Ms) value because of the interface roughness between the two layers. The other is a search for the most suitable materials with high perpendicular magnetic anisotropy in order to have high thermal stability. In this work, we present an amorphous ferromagnetic Co75Si15B10 material and compare the magnetic properties of a [CoSiB (0.3, 0.4, 0.5 nm)/Pt (1.4 nm)]5 multilayer and new combinations [CoSiB (0.3, 0.4, 0.5 nm)/Au (1.5 nm)]5.

Perpendicular Magnetic Anisotropy of CoSiB/Pt Multilayers

We have investigated the perpendicular magnetic anisotropy of [CoSiB tCoSiB/Pt tPt]n multilayers as a function of the CoSiB and the Pt thicknesses and the number of repetition of the CoSiB/Pt bilayers. The coercivity (Hc) and the saturation magnetization (Ms) of the amorphous ferromagnetic material Co75Si15B10 were taken to be 1.6 Oe and 407 emu/cm , respectively. The Hc in [CoSiB tCoSiB/Pt 14 A]5 multilayers increases with increasing tCoSiB to reach a maximum at tCoSiB = 3 A and then decreases for tCoSiB > 3 A. The highest Hc of 224 Oe and the highest perpendicular magnetic anisotropy Ku of 2 × 10 erg/cm were obtained in the [CoSiB 3 A/Pt 14 A]5 multilayer. Additional Pt layers do not contribute to the perpendicular magnetic anisotropy. The single-domain structure evolves into a striped multidomain structure as the bilayer repetition number n increases above 6.

Magnetic properties of micro- and nanowires in the superhigh-frequency range

The skin-effect theory is presented using the example of an amorphous ferromagnetic material taking into account the ferromagnetic resonance. The theoretical dependence of the impedance of a microwire on its magnetic permeability is determined. The results allow analyzing experiments on studying the high-frequency properties of amorphous microwires.

An Integrated Micro-Fluxgate Magnetic Sensor With Front-End Circuitry

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> In this paper, a double-axis planar micro-Fluxgate magnetic sensor and its front-end circuitry are presented. The ferromagnetic core material, i.e., the Vitrovac 6025 X, has been deposited on top of the coils with the dc-magnetron sputtering technique, which is a new type of procedure with respect to the existing solutions in the field of Fluxgate sensors. This procedure allows us to obtain a core with the good magnetic properties of an amorphous ferromagnetic material, which is typical of a core with 25-<formula formulatype="inline"><tex Notation="TeX">$\mu \hbox{m}$</tex></formula> thickness, but with a thickness of only 1 <formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$ </tex></formula>, which is typical of an electrodeposited core. The micro-Fluxgate has been realized in a 0.5- <formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> CMOS process using copper metal lines to realize the excitation coil and aluminum metal lines for the sensing coil, whereas the integrated interface circuitry for exciting and reading out the sensor has been realized in a 0.35-<formula formulatype="inline"><tex Notation="TeX">$\mu\hbox{m}$ </tex></formula> CMOS technology. Applying a triangular excitation current of 18 mA peak at 100 kHz, the magnetic sensitivity achieved is about 10 <formula formulatype="inline"><tex Notation="TeX">$\hbox{LSB}/\mu\hbox{T}$</tex></formula> [using a 13-bit analog-to-digital converter (ADC)], which is suitable for detecting the Earth's magnetic field <formula formulatype="inline"><tex Notation="TeX">$(\pm 60\ \mu\hbox{T})$</tex></formula>, whereas the linearity error is 3% of the full scale. The maximum angle error of the sensor evaluating the Earth magnetic field is 2 <formula formulatype="inline"><tex Notation="TeX">$^{\circ}$</tex></formula>. The power consumption of the sensor is about 13.7 mW. The total power consumption of the system is about 90 mW. </para>

Bias voltage dependence of magnetic tunnel junctions comprising amorphous ferromagnetic CoFeSiB layer with double barriers

AbstractDouble‐barrier magnetic tunnel junctions (DMTJs) with and without an amorphous ferromagnetic material such as CoFeSiB 10, CoFe 5/CoFeSiB 5, and CoFe 10 (nm) were prepared and compared to investigate the bias voltage dependence of the tunneling magnetoresistance (TMR) ratio. Typical DMTJ structures were Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlOx /free layer 10/AlOx /CoFe 7/IrMn 10/Ru 60 (in nanometers). The interlayer coupling field and the normalized TMR ratios at the applied voltages of +0.4 and –0.4 V of the amorphous CoFeSiB free‐layer DMTJ offer lower and higher values than that of the polycrystalline CoFe free‐layer DMTJ, respectively. An amorphous ferromagnetic CoFeSiB layer improves the interface roughness of the free layer/tunnel barrier and, as a result, the interlayer coupling field and bias voltage dependence of the TMR ratio are suppressed at a given voltage. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Advanced process of the magnetic core integration for the micro fluxgate magnetometer

We present improved processing of the soft amorphous ferromagnetic material for the fully integrated fluxgate magnetometer. The additional steps of polishing, chemical thinning and annealing are introduced to preserve the original material characteristics and increase the sensor fabrication yield. At the same time, due to the reduced thickness, the eddy current losses and skin effect are decreased. Hysteresis and power loss, as a measure of the magnetic material condition, are acquired after each processing step. Prepared material has at least 10-times better characteristics than electroplated NiFe. Presented procedure is compatible with the CMOS technology and implemented on a whole wafer in a batch process to form the cores for a low power magnetic sensor.

Undergraduate laboratory demonstration of aspects of phase transitions using Curie temperature determination in amorphous ferromagnetic materials

Traditionally, Curie temperature measurements have been performed using a vibrating sample magnetometer, an expensive piece of equipment not readily available to all undergraduate physics laboratories. This article describes an alternative measurement technique requiring only equipment stocked in most undergraduate physics departments. The device was originally constructed for data collection as part of a graduate-level research program in radiation damage effects in amorphous Fe–Ni–P–B ferromagnetic alloys, but can be used for lecture demonstration purposes or as an undergraduate laboratory experiment.

Stress sensitivity coefficient in polycrystalline and amorphous ferromagnetic materials below room temperature

The piezomagnetic coupling coefficient (the «stress sensitivity») is quantitatively investigated below room temperature and a comparison is made among polycrystalline samples and amorphous ones. The technique used is an original one. It experimentally consists in the measurement of the amplitude of magnetoelastic waves, their resonance frequency and differential susceptibility; theoretically, it consists in coupling Newton’s law of force with the piezomagnetic state equations. The results clearly show different responses of polycrystalline samples with respect to the amorphous ones; in particular the nonmonotonic behaviour of the «stress sensitivity» for metallic glasses is interesting for establishing their actual magnetic states at low temperature.

Giant magneto-optic rotation in amorphous uranium antimonide (invited)

Amorphous U-Sb alloys in the vicinity of the composition U3Sb4 have magneto-optic Faraday rotations of + 2 × 106 deg/cm. This is the highest rotation of any amorphous ferromagnetic material. These alloys also have relatively high Curie temperatures of about 140 K with magnetic moments per uranium of up to 1.4μB. These properties are unexpected since it is known from intermetallic compounds that U atoms must be isolated from each other in order to develop a magnetic moment. In a concentrated random amorphous alloy, no magnetic moment on the uranium would be expected because of the high probability of uranium near neighbors. In the U-Sb amorphous alloys, however, there appears to be chemical short-range order which tends to favor Sb nearest neighbors for uranium. The amorphous U-Sb alloys have Kerr rotations of about −3°. This value is comparable in magnitude but opposite in sign to that of the single-crystal rock salt compound USb in the visible. In these amorphous alloys the Hall angle from the spontaneous Hall effect can be as much as 17°. Similar large magneto-optic and Hall coefficients have also been found in amorphous U-Bi, U-Sb-Mn, and U-Sb-Co alloys.

Induced anisotropies in ferromagnetic amorphous ribbons locally annealed by laser.

The origin of anisotropy induced by local laser annealing has been studied in amorphous ferromagnetic materials with different magnetostriction constants. The results have been explained using a theoretical model based on the assumption that the origin of the induced anisotropies are internal stresses produced by inhomogeneous heat flows during the local laser annealing. The induced anisotropies are not uniform, which produces a magnetostatic energy that can modify the induced magnetoelastic anisotropy. This effect can be used to induce different anisotropies by changing the shape of the local laser annealing.