scholarly journals Orthogonal interlayer coupling in an all-antiferromagnetic junction

2021 ◽  
Author(s):  
Yongjian Zhou ◽  
Liyang Liao ◽  
Tingwen Guo ◽  
Hua Bai ◽  
Mingkun Zhao ◽  
...  
Keyword(s):  
High Speed ◽  
Giant Magnetoresistance ◽  
Spin Dynamics ◽  
Magnetic Ordering ◽  
Functional Materials ◽  
Interlayer Coupling ◽  
Information Storage ◽  
Stray Field ◽  
Potential Candidate ◽  
Ultrahigh Density

Abstract The interlayer coupling of two ferromagnetic layers results in found of giant magnetoresistance, which forms the foundation of spintronics and accelerates the development of information technology. Compared with ferromagnets, antiferromagnets (AFMs) possess huge potential in ultrafast and high-density data processing and information storage because of their terahertz spin dynamics and subtle stray field. The interlayer coupling in AFMs has long been neglected, because the collinear parallel and antiparallel arrangements of AFMs are indistinguishable. However, the noncollinear interlayer coupling in AFMs is detectable, and can be a potential candidate for practical antiferromagnetic spintronic devices. Here we demonstrate orthogonal interlayer coupling at room temperature in an all-antiferromagnetic junction Fe2O3/Cr2O3/Fe2O3, where the Néel vectors in the top and bottom functional materials Fe2O3 are strongly orthogonally coupled and the coupling strength of which is significantly affected by the thickness of the antiferromagnetic Cr2O3 spacer. From the energy and symmetry analysis, the direct coupling via uniform magnetic ordering is excluded. The coupling is proposed to be mediated by quasi-long range order in the spacer. Besides the fundamental significance, the strong coupling in an antiferromagnetic junction makes it a promising building block for practical antiferromagnetic spintronics with high-speed operation and ultrahigh-density integration.

scholarly journals All-optical demultiplexing of closely spaced multimedia radio signals using sub-picometer fiber Bragg grating

2021 ◽  
Author(s):  
Hatice Kosek
Keyword(s):  
Wireless Lan ◽  
High Speed ◽  
Bandpass Filter ◽  
Optical Filters ◽  
Multimedia Data ◽  
Potential Candidate ◽  
Rf Signals ◽  
All Optical ◽  
Radio Signals ◽  
Network Flexibility

Subcarrier multiplexed (SCM) transmission of multimedia radio signals such as CATV (5-860 MHz), cellular wireless (900 MHz) and wireless LAN (2.4 GHz) over fiber is frequently used to deliver broadband services cost effectively. These multi-channel radio-over-fiber (ROF) links have interesting applications and can connect enhanced wireless hotspots that will support high speed wireless LAN services or low speed cellular services to different customers from the same antenna. The SCM signals need to be demultiplexed, preferably in the optical domain for many reasons. Prefiltering of SCM signals with fiber-based optical filters warrants the use of inexpensive photodetectors and increases network flexibility. However, realizing optical demultiplexing as sub-GHz level is challenging and thus necessitates optical filters with high selectivity and low insertion loss and distortion. We developed a novel sub-picometer all-optical bandpass filter by creating a resonance cavity using two closely matched fiber Bragg gratings (FBGs). This filter has a bandwidth of 120 MHz at -3 dB, 360 MHz at -10 dB and 1.5 GHz at -20 dB. Experimental results showed that the filter is capable of separating two radio frequency (RF) signals spaced as close as 50 MHz without significant distortion. When this demultiplexer was employed to optically separate 2.4 GHz and 900 MHz radio signals, it was found to be linear from -38 dBm to +6 dBm with ~ 25.5 dB isolation. There was no significant increment in the BER of the underlying multimedia data. Results verified that the fabricated narrow bandpass filter can be a potential candidate in demultiplexing of RF signals in networks based on subcarrier multiplexed schemes.

scholarly journals Stray-field-induced modification of coherent spin dynamics

2007 ◽  
Author(s):  
L. Meier ◽  
G. Salis ◽  
C. Ellenberger ◽  
E. Gini ◽  
K. Ensslin
Keyword(s):  
Spin Dynamics ◽  
Stray Field ◽  
Coherent Spin

Giant magnetoresistance and interlayer coupling in Cu(111)/Ag67Co33 granular multilayers

1997 ◽  
Vol 81 (8) ◽  
pp. 4589-4591 ◽  
Author(s):  
Yuansu Luo ◽  
Michael Moske ◽  
Andrea Kaeufler ◽  
Tilmann Lorenz ◽  
Konrad Samwer
Keyword(s):  
Giant Magnetoresistance ◽  
Interlayer Coupling

scholarly journals Magnetic ordering and spin dynamics in potassium jarosite: A Heisenberg kagomé lattice antiferromagnet

2003 ◽  
Vol 67 (22) ◽  
Author(s):  
Masahide Nishiyama ◽  
Satoru Maegawa ◽  
Toshiya Inami ◽  
Yoshio Oka
Keyword(s):  
Spin Dynamics ◽  
Magnetic Ordering ◽  
Kagome Lattice ◽  
Kagomé Lattice

scholarly journals Micromagnetic Simulations of Submicron Vortex Structures for the Detection of Superparamagnetic Labels

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5819
Author(s):  
Lukas Wetterau ◽  
Claas Abert ◽  
Dieter Suess ◽  
Manfred Albrecht ◽  
Bernd Witzigmann
Keyword(s):  
Electric Potential ◽  
Giant Magnetoresistance ◽  
Spin Diffusion ◽  
Magnetic Vortex ◽  
Electric Response ◽  
Stray Field ◽  
Soft Magnetic ◽  
Micromagnetic Simulations ◽  
Gmr Sensor ◽  
Magnetization Change

We present a numerical investigation on the detection of superparamagnetic labels using a giant magnetoresistance (GMR) vortex structure. For this purpose, the Landau–Lifshitz–Gilbert equation was solved numerically applying an external z-field for the activation of the superparamagnetic label. Initially, the free layer’s magnetization change due to the stray field of the label is simulated. The electric response of the GMR sensor is calculated by applying a self-consistent spin-diffusion model to the precomputed magnetization configurations. It is shown that the soft-magnetic free layer reacts on the stray field of the label by shifting the magnetic vortex orthogonally to the shift direction of the label. As a consequence, the electric potential of the GMR sensor changes significantly for label shifts parallel or antiparallel to the pinning of the fixed layer. Depending on the label size and its distance to the sensor, the GMR sensor responds, changing the electric potential from 26.6 mV to 28.3 mV.

Sub-200 Oe Giant Magnetoresistance in Manganite Tunnel Junctions

1997 ◽  
Vol 494 ◽  
Author(s):  
Gang Xiao ◽  
A. Gupta ◽  
X. W. Li ◽  
G. Q. Gong ◽  
J. Z. Sun
Keyword(s):  
Electronic Structure ◽  
Colossal Magnetoresistance ◽  
Giant Magnetoresistance ◽  
Domain Walls ◽  
Tunnel Junctions ◽  
Research Effort ◽  
Boundary Effect ◽  
Magnetic Domain ◽  
Magnetic Ordering ◽  
Dependent Transport

ABSTRACTMetallic manganite oxides, La1-xDxMnO3 (D=Sr, Ca, etc.), display “colossal” magnetoresistance (CMR) near their magnetic phase transition temperatures (Tc) when subject to a Tesla-scale magnetic field. This phenomenal effect is the result of the strong interplay inherent in this class of materials among electronic structure, magnetic ordering, and lattice dynamics. Though fundamentally interesting, the CMR effect achieved only at large fields poses severe technological challenges to potential applications in magnetoelectronic devices, where low field sensitivity is crucial. Among the objectives of our research effort involving manganite materials is to reduce the field scale of MR by designing and fabricating tunnel junctions and other structures rich in magnetic domain walls. The junction electrodes were made of doped manganite epitaxial films, and the insulating barrier of SrTiO3. The interfacial expitaxy has been imaged by using high-resolution transmission electron microscopy (TEM). We have used self-aligned lithographic process to pattern the junctions to micron scale in size. Large MR values close to 250% at low fields of a few tens of Oe have been observed. The mechanism of the spin-dependent transport is due to the spin-polarized tunneling between the half-metallic electrodes, in which the spins of the conduction electrons are nearly fully polarized. We will present results of field and temperature dependence of MR in these structures and discuss the electronic structure of the manganite inferred from tunneling measurement. Results of large MR at low fields due to the grain-boundary effect will also be presented.

Neutrons Not Entitled to Retire at the Age of 60: More than Ever Needed to Reveal Magnetic Structures

2011 ◽  
Vol 170 ◽  
pp. 263-269 ◽  
Author(s):  
Clemens Ritter
Keyword(s):  
Rare Earth ◽  
Giant Magnetoresistance ◽  
High Temperature Superconductivity ◽  
Functional Materials ◽  
Symmetry Analysis ◽  
Magnetic Shape Memory ◽  
Magnetic Structures ◽  
Magnetic Symmetry ◽  
The Rare Earth

In 1949 Shull et al. [1] used for the first time neutrons for the determination of a magnetic structure. Ever since, the need for neutrons for the study of magnetism has increased. Two main reasons can be brought forward to explain this ongoing success: First of all a strong rise in research on functional materials (founding obliges) and secondly the increasing availability of easy to use programmes for the treatment of magnetic neutron diffraction data. The giant magnetoresistance effect, multiferroic materials, magnetoelasticity, magnetic shape memory alloys, magnetocaloric materials, high temperature superconductivity or spin polarized half metals: The last 15 years have seen the event of all these “hot topics” where the knowledge of the magnetism is a prerequisite for understanding the underlying functional mechanisms. Refinement programs like FULLPROF or GSAS and programs for magnetic symmetry analysis like BASIREPS or SARAH make the determination of magnetic structures accessible for non specialists. Following a historical overview on the use of neutron powder diffraction for the determination of magnetic structures, I will try to convince you of the easiness of using magnetic symmetry analysis for the determination of magnetic structures using some recent examples of own research on the rare earth iron borate TbFe3(BO3)4 and the rare earth transition metal telluride Ho6FeTe2.

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