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. 

scholarly journals A model of the response of GMR of metallic multilayers to external magnetic field

2015 ◽  
Vol 33 (4) ◽  
pp. 835-840
Author(s):  
J.I. Uba ◽  
A.J. Ekpunobi ◽  
P.I. Ekwo
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Giant Magnetoresistance ◽  
Ion Beam ◽  
Interface Roughness ◽  
Total Density ◽  
Metallic Multilayers ◽  
Interface Quality ◽  
Qualitative Measure

AbstractIt has not been possible to transform resistivity models in terms of magnetic field in order to account for variation of giant magnetoresistance (GMR) with external magnetic field, which would have led to determination of material properties. This problem is approached mathematically via variation calculus to arrive at an exponential function that fits observed GMR values. Using this model in free electron approximation, the mean Fermi vector, susceptibility and total density of states of a number of metallic multilayers are determined from their reported GMR values. Susceptibility is found to depend on interface roughness and antiferromagnetic (AF) coupling; thus, it gives qualitative measure of interface quality and AF coupling. Comparison of susceptibilities and GMRs of electrodeposited and ion beam sputtered Co/Cu structures shows that a rough interface suppresses GMR in the former but enhances it in the latter.

scholarly journals Broad band infrared modulation using spintronic-plasmonic metasurfaces

Nanophotonics ◽  
2019 ◽  
Vol 8 (10) ◽  
pp. 1847-1854 ◽  
Author(s):  
Gaspar Armelles ◽  
Luca Bergamini ◽  
Nerea Zabala ◽  
María Ujué González ◽  
Fernando García ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Electrical Resistivity ◽  
External Magnetic Field ◽  
Spectral Range ◽  
Giant Magnetoresistance ◽  
Optical Constants ◽  
Broad Band ◽  
Resonance Wavelength ◽  
Wide Spectral Range ◽  
Direct Fabrication

AbstractWe present magnetic field induced modulation of the optical response of slit plasmonic metasurfaces fabricated out of giant magnetoresistance/spintronic materials in the 2–17 μm spectral range of the spectrum. The modulation of the slit plasmonic modes is due to the modification of the electrical resistivity (and, in turn, of the optical constants) induced by the application of an external magnetic field. This modulation is found to continuously increase both with the slit concentration and with the slit resonance wavelength, with a prospective further increase for wavelengths of up to 60–80 μm. The direct fabrication and implementation of the modulation setup opens a competitive route for the development of active plasmonic metasurfaces in a wide spectral range.

The Formation Energy of Martensite Nuclei and the Phase Transition Kinetics under the Action of an External Magnetic Field

2021 ◽  
Vol 410 ◽  
pp. 3-8
Author(s):  
Viktor N. Pustovoit ◽  
Yuri V. Dolgachev
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Initial Phase ◽  
Formation Energy ◽  
Martensite Phase ◽  
Nucleation Center ◽  
Austenite Matrix ◽  
Ferromagnetic Order ◽  
The Matrix ◽  
Phase Transition Kinetics

The formation energy of martensite nuclei in the austenite matrix is calculated. Nanoclusters with ferromagnetic order, which exist in austenite above the Curie temperature, reduce the formation energy of a critical martensite nucleation center when exposed to an external magnetic field. The data obtained are explained by the magnetic separation of the initial phase under the action of a magnetic field. A fluctuation increase in nanovolumes with a ferromagnetic order in austenite increases the energy in a atoms group of the matrix phase with a parallel spins arrangement. As a result, the nucleation rate of the martensite phase increases and the martensitic transformation proceeds more completely.

scholarly journals The Effect of an External Magnetic Field on the Aspect Ratio and Heat Input of Gas-Metal-Arc-Welded AZ31B Alloy Weld Joints Using a Response Surface Methodology

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5269
Author(s):  
Pankaj Sharma ◽  
Somnath Chattopadhyaya ◽  
Nirmal Kumar Singh ◽  
Marta Bogdan-Chudy ◽  
Grzegorz Krolczyk
Keyword(s):  
Magnetic Field ◽  
Response Surface Methodology ◽  
External Magnetic Field ◽  
Aspect Ratio ◽  
Response Surface ◽  
Heat Input ◽  
Feed Rate ◽  
Gas Flow ◽  
Gas Metal Arc Welding ◽  
Weld Joints

This study attempted to analyze and optimize the effect of an external magnetic field (EMF) on the aspect ratio and heat input for AZ31B weld joints that were welded using the gas metal arc welding (GMAW) process. The response surface methodology (RSM) was adopted for the critical analysis, and subsequently, mathematical models were developed based on the experimental results. It was observed that the EMF and its interaction with the wire feed rate significantly affected the aspect ratio and heat input, respectively. At 119 G (magnetic field), 700 mm/min (welding speed), 5.8 m/min feed rate, and 11.5 L/min (gas flow rate), the aspect ratio was 2.26, and the corresponding heat input factor (HIf) was 0.8 with almost full weld penetration.

Energy Absorption/Dissipation Performances of Magnetic-Sensitive Rubber (MSR) With Hollow Iron Balls

2015 ◽  
Author(s):  
Shengqiang Zhang ◽  
Lingyu Sun ◽  
Dingxin Leng ◽  
Bincheng Huang ◽  
Jun Xu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Energy Absorption ◽  
Strain Energy ◽  
Effective Strain ◽  
Stress Concentrations ◽  
Buffer Material ◽  
The Matrix ◽  
Thin Walled ◽  
Applied External Magnetic Field

A kind of novel smart buffer material, magnetic-sensitive rubber (MSR) with embedded thin-walled iron balls, is provided, and the energy absorption and energy dissipation properties are investigated numerically. Two kinds of representative volume elements (RVEs) of MSR specimens with solid or hollow iron balls are studied, respectively. Under uniaxial compression alone or combined with magnetic field, the relation between effective stress and effective strain and that between strain energy desity and total compression deformation for these two specimens are established, respectively. With the increase of strain, it is demonstrated numerically that the MSRs with hollow iron balls have better energy absorption/dissipation capability than previous MSRs with solid balls. And the applied external magnetic-field increases this capability more. Under compression, the stress concentrations in elastomer matrix around the hollow balls decrease, that could increase the ultimate compression loads before the matrix failures. This is beneficial for us to design lightweight and efficient buffers according to different application cases.

scholarly journals Correlation between Ferromagnetic Layer Easy Axis and the Tilt Angle of Self Assembled Chiral Molecules

Molecules ◽  
2020 ◽  
Vol 25 (24) ◽  
pp. 6036
Author(s):  
Nir Sukenik ◽  
Francesco Tassinari ◽  
Shira Yochelis ◽  
Oded Millo ◽  
Lech Tomasz Baczewski ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Tilt Angle ◽  
Easy Axis ◽  
Ferromagnetic Layer ◽  
Clear Correlation ◽  
Chiral Molecules ◽  
Axis Direction ◽  
Out Of Plane ◽  
Magnetic Substrate

The spin–spin interactions between chiral molecules and ferromagnetic metals were found to be strongly affected by the chiral induced spin selectivity effect. Previous works unraveled two complementary phenomena: magnetization reorientation of ferromagnetic thin film upon adsorption of chiral molecules and different interaction rate of opposite enantiomers with a magnetic substrate. These phenomena were all observed when the easy axis of the ferromagnet was out of plane. In this work, the effects of the ferromagnetic easy axis direction, on both the chiral molecular monolayer tilt angle and the magnetization reorientation of the magnetic substrate, are studied using magnetic force microscopy. We have also studied the effect of an applied external magnetic field during the adsorption process. Our results show a clear correlation between the ferromagnetic layer easy axis direction and the tilt angle of the bonded molecules. This tilt angle was found to be larger for an in plane easy axis as compared to an out of plane easy axis. Adsorption under external magnetic field shows that magnetization reorientation occurs also after the adsorption event. These findings show that the interaction between chiral molecules and ferromagnetic layers stabilizes the magnetic reorientation, even after the adsorption, and strongly depends on the anisotropy of the magnetic substrate. This unique behavior is important for developing enantiomer separation techniques using magnetic substrates.

scholarly journals Observation of anti-damping spin-orbit torques generated by in-plane and out-of-plane spin polarizations in MnPd3

2021 ◽  
Author(s):  
Mahendra DC ◽  
Ding-Fu Shao ◽  
Vincent Hou ◽  
Patrick Quarterman ◽  
Ali Habiboglu ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Films ◽  
External Magnetic Field ◽  
Spin Polarization ◽  
Density Functional ◽  
Ferromagnetic Layer ◽  
Magnetic Memory ◽  
Spin Orbit ◽  
Logic Devices ◽  
Out Of Plane

Abstract High spin-orbit torques (SOTs) generated by topological materials and heavy metals interfaced with a ferromagnetic layer show promise for next generation magnetic memory and logic devices. SOTs generated from the in-plane spin polarization along y-axis originated by the spin Hall and Edelstein effects can switch magnetization collinear with the spin polarization in the absence of external magnetic fields. However, an external magnetic field is required to switch the magnetization along x and z-axes via SOT generated by y-spin polarization. Here, we present that the above limitation can be circumvented by unconventional SOT in magnetron-sputtered thin film MnPd3. In addition to the conventional in-plane anti-damping-like torque due to the y-spin polarization, out-of-plane and in-plane anti-damping-like torques originating from z-spin and x-spin polarizations, respectively have been observed at room temperature. The spin torque efficiency (θ_y) corresponding to the y-spin polarization from MnPd3 thin films grown on thermally oxidized silicon substrate and post annealed at 400 ℃ is 0.34 - 0.44 while the spin conductivity (σ_zx^y) is ~ 5.70 – 7.30× 105 ℏ⁄2e Ω-1m-1. Remarkably, we have demonstrated complete external magnetic field-free switching of perpendicular Co layer via unconventional out-of-plane anti-damping-like torque from z-spin polarization. Based on the density functional theory calculations, we determine that the observed x- and z- spin polarizations with the in-plane charge current are due to the low symmetry of the (114) oriented MnPd3 thin films. Taken together, the new material reported here provides a path to realize a practical spin channel in ultrafast magnetic memory and logic devices.

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