Improvement of Gmr in NiFeCo/Cu Multilayers by a Layer - by - Layer Magnetic Field Sputtering

1995 ◽  
Vol 384 ◽  
Author(s):  
K. Saito ◽  
Y. Yanagida ◽  
Y. Obi ◽  
H. Itoho ◽  
H. Fujimori
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Domain Wall ◽  
Giant Magnetoresistance ◽  
High Sensitivity ◽  
Sputter Deposition ◽  
Spin Rotation ◽  
Layer By Layer ◽  
Wall Movement ◽  
Magnetic Layers

ABSTRACTNiFeCo/Cu multilayers fabricated by an improved magnetic field sputtering were investigated in order to achieve the soft GMR (giant magnetoresistance) with a high sensitivity at low magnetic fields. A magnetic field was applied to the film during sputter-deposition, and its field direction was changed alternately from layer to layer. Such an alternate field sputtering is called hereafter layer-by-layer magnetic field sputtering. The best GMR characteristics (large MR at low magnetic fields) were achieved when the angle between the directions of magnetic field applied to neighboring two magnetic layers was 90°. As one of the speculation, it has been considered that the result is attributed to the induced composite magnetic anisotropy which causes the magnetization to occur more dominantly by spin rotation than by domain wall movement.

LOW-FIELD INHOMOGENEITY-INDUCED MAGNETORESISTANCE IN SILICON

SPIN ◽  
2012 ◽  
Vol 02 (01) ◽  
pp. 1250002 ◽  
Author(s):  
XIAOZHONG ZHANG ◽  
CAIHUA WAN
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Giant Magnetoresistance ◽  
High Sensitivity ◽  
Boundary Region ◽  
Charge Carriers ◽  
Silicon Devices ◽  
Low Field ◽  
Silicon Based ◽  
The Magnetic Field

We show that inhomogeneity-induced magnetoresistance (IMR) in lightly doped silicon can be significantly enhanced through the injection of minority charge carriers, and then tuned by an applied current to have an onset at low magnetic fields. We designed an IMR device in which, the inhomogeneity is provided by the p–n boundary formed between regions where conduction is dominated by the minority and majority charge carriers respectively; application of a magnetic field distorts the current in the boundary region, resulting in large magnetoresistance. The room-temperature field sensitivity of our IMR device at low fields was remarkably improved, with magnetoresistance reaching 10% at 0.07 T and 100% at 0.2 T, approaching the performance of commercial giant magnetoresistance devices. The combination of high sensitivity to low magnetic fields and large high-field response should make this device concept attractive to the magnetic field sensing industry. Moreover, being based on a conventional silicon platform, it should be possible to integrate with existing silicon devices and so aid the development of silicon-based magnetoelectronics.

Radio Measurements of Coronal Magnetic Fields

1994 ◽  
Vol 144 ◽  
pp. 21-28 ◽  
Author(s):  
G. B. Gelfreikh
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Solar Corona ◽  
Active Regions ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Transverse Magnetic ◽  
Radio Sources ◽  
Radio Waves ◽  
Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

scholarly journals Correlation of composition, aspect ratio and magnetic resistance of multilayer micro- and nanowires of the “ferromagnetic / diamagnetic” type

Doklady BGUIR ◽  
2021 ◽  
Vol 19 (2) ◽  
pp. 5-13
Author(s):  
V. M. Fedosyuk
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Aspect Ratio ◽  
Aluminum Oxide ◽  
Giant Magnetoresistance ◽  
Pore Diameter ◽  
Ferromagnetic Layer ◽  
Type I ◽  
Magnetic Layers ◽  
The Matrix

 The results of study of the giant magnetoresistance coefficient (GMR) in multilayer micro- and nanowires based on successively alternating ferromagnetic (Co, CoNi and NiFe) and diamagnetic (Cu) layers are presented in the paper. The samples were obtained by electrochemical deposition into the matrix pores. Aluminum oxide was used as matrices. To establish the influence of the aspect ratio, matrices of two types were used: with a pore diameter of 8 µm and 170–200 nm and a variable thickness from 10 to 60 µm. Investigations of the GMR coefficient were carried out by measuring the current-voltage characteristics in external magnetic fields up to 130 mT. When using type I matrices (pore diameter 8 μm), a positive GMR coefficient (an increase in electrical resistivity in an external magnetic field) was noted, while when using type II matrices (pore diameter 170–200 nm), a negative GMR coefficient was established (a decrease in electrical resistance in an external magnetic field). This is due to the enhancement of the interactions of spin-polarized electrons in the magnetic layers through the copper layer through the RKKY exchange with an increase in the aspect ratio. A significant effect of the composition of the ferromagnetic layer (Co, CoNi, and NiFe) on the value  of the GMR coefficient is noted. The maximum value of the negative GMR coefficient (up to –27.5 %) was established for the CoNi-based nanowire system. The use of multilayer micro- and nanowires, electrolytically deposited in a matrix of aluminum oxide with the ability to control the GMR coefficients, opens up perspective use of these objects as sensitive elements (sensors) of a constant magnetic field, as well as devices for storing magnetic information with a vertical principle. 

Growth and Observation of Low-Field Giant Magnetoresistance in La0.7Sr0.3MnO3/ZnO Superlattice Structures

2006 ◽  
Vol 6 (3) ◽  
pp. 612-617
Author(s):  
Ashutosh Tiwari ◽  
J. Narayan
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Giant Magnetoresistance ◽  
Pulsed Laser ◽  
Laser Deposition ◽  
Deposition Technique ◽  
New Class ◽  
Superlattice Structure ◽  
Low Field ◽  
Superlattice Structures

We report the growth of a new class of superlattice structure, consisting of alternate layers of La0.7Sr0.3MnO3 (LSMO) and ZnO, which exhibits giant magnetoresistance at low fields. These superlattices were fabricated using a novel pulsed-laser deposition technique with a specially designed target assembly. Giant magnetoresistance of >250% has been observed in these structures in current-in-plane configuration on the application of just ∼400 Gauss of magnetic field over the broad temperature range 15–200 K. Observation of giant magnetoresistance at such low magnetic fields is a groundbreaking step in the field of novel magnetic materials and devices.

scholarly journals Low Field Optimization of a Non-Contacting High-Sensitivity GMR-Based DC/AC Current Sensor

Sensors ◽  
2021 ◽  
Vol 21 (7) ◽  
pp. 2564
Author(s):  
Cristian Mușuroi ◽  
Mihai Oproiu ◽  
Marius Volmer ◽  
Jenica Neamtu ◽  
Marioara Avram ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Giant Magnetoresistance ◽  
Detection System ◽  
High Sensitivity ◽  
Practical Method ◽  
Current Transformer ◽  
Current Sensor ◽  
Temperature Drift ◽  
Planar Coil ◽  
Gmr Sensor

Many applications require galvanic isolation between the circuit where the current is flowing and the measurement device. While for AC, the current transformer is the method of choice, in DC and, especially for low currents, other sensing methods must be used. This paper aims to provide a practical method of improving the sensitivity and linearity of a giant magnetoresistance (GMR)-based current sensor by adapting a set of design rules and methods easy to be implemented. Our approach utilizes a multi-trace current trace and a double differential GMR based detection system. This essentially constitutes a planar coil which would effectively increase the usable magnetic field detected by the GMR sensor. An analytical model is developed for calculating the magnetic field generated by the current in the GMR sensing area which showed a significant increase in sensitivity up to 13 times compared with a single biased sensor. The experimental setup can measure both DC and AC currents between 2–300 mA, with a sensitivity between 15.62 to 23.19 mV/mA, for biasing fields between 4 to 8 Oe with a detection limit of 100 μA in DC and 100 to 300 μA in AC from 10 Hz to 50 kHz. Because of the double differential setup, the detection system has a high immunity to external magnetic fields and a temperature drift of the offset of about −2.59 × 10−4 A/°C. Finally, this setup was adapted for detection of magnetic nanoparticles (MNPs) which can be used to label biomolecules in lab-on-a-chip applications and preliminary results are reported.

scholarly journals Superconductor–insulator transition in two-dimensional indium–indium-oxide composite

2020 ◽  
Vol 118 (2) ◽  
pp. e2015970118
Author(s):  
Bar Hen ◽  
Xinyang Zhang ◽  
Victor Shelukhin ◽  
Aharon Kapitulnik ◽  
Alexander Palevski
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Indium Oxide ◽  
Hybrid System ◽  
Giant Magnetoresistance ◽  
Vacuum Annealing ◽  
Quantum Criticality ◽  
Insulator Transition ◽  
Cooper Pairs ◽  
The Magnetic Field

The magnetic-field–tuned superconductor-to-insulator transition was studied in a hybrid system of superconducting indium islands, deposited on an indium oxide (InOx) thin film, which exhibits global superconductivity at low magnetic fields. Vacuum annealing was used to tune the conductivity of the InOx film, thereby tuning the inergrain coupling and the nature of the transition. The hybrid system exhibits a “giant” magnetoresistance above the magnetic-field–tuned superconductor-to-insulator transition (H-SIT), with critical behavior similar to that of uniform InOx films but at much lower magnetic fields, that manifests the duality between Cooper pairs and vortices. A key feature of this hybrid system is the separation between the quantum criticality and the onset of nonequilibrium behavior.

scholarly journals Microwave Depolarization above Sunspots

2010 ◽  
Vol 6 (S273) ◽  
pp. 487-490
Author(s):  
Jeongwoo Lee ◽  
Stephen M. White
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Current Density ◽  
Current Density Distribution ◽  
High Sensitivity ◽  
Coronal Magnetic Field ◽  
Magnetic Polarity ◽  
Very Large Array ◽  
Density Maps ◽  
Polarity Inversion Line

AbstractMicrowave emissions from sunspots are circularly polarized in the sense of rotation (right or left) determined by the polarity (north or south) of coronal magnetic fields. However, they may convert into unpolarized emissions under certain conditions of magnetic field and electron density in the corona, and this phenomenon of depolarization could be used to derive those parameters. We propose another diagnostic use of microwave depolarization based on the fact that an observed depolarization strip actually represents the coronal magnetic polarity inversion line (PIL) at the heights of effective mode coupling, and its location itself carries information on the distribution of magnetic polarity in the corona. To demonstrate this diagnostic utility we generate a set of magnetic field models for a complex active region with the observed line-of-sight magnetic fields but varying current density distribution and compare them with the 4.9 GHz polarization map obtained with the Very Large Array (VLA). The field extrapolation predicts very different locations of the depolarization strip in the corona depending on the amount of electric currents assumed to exist in the photosphere. Such high sensitivity of microwave depolarization to the coronal magnetic field can therefore be useful for validating electric current density maps inferred from vector magnetic fields observed in the photosphere.

scholarly journals Magnetic Field Sensor Based on a Tri-Microfiber Coupler Ring in Magnetic Fluid and a Fiber Bragg Grating

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5100 ◽  
Author(s):  
Wei ◽  
Liu ◽  
Mallik ◽  
Farrel ◽  
Wu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Fiber Bragg Grating ◽  
Magnetic Fluid ◽  
High Sensitivity ◽  
Spectral Shift ◽  
Magnetic Field Sensor ◽  
Bragg Grating ◽  
Low Field ◽  
Field Sensor

In this paper we propose and investigate a novel magnetic field sensor based on a Tri-microfiber coupler combined with magnetic fluid and a fiber Bragg grating (FBG) in a ring. A sensitivity of 1306 pm/mT was experimentally demonstrated in the range of magnetic fields from 0 to 15 mT. The reflection peak in the output spectrum associated with the FBG serves as a reference point allowing to avoid ambiguity in determining the spectral shift induced by the magnetic field. Due to its high sensitivity at low magnetic fields, the proposed structure could be of high interest in low field biosensing applications that involve a magnetic field, such as magnetic manipulation or separation of biomolecules.

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