scholarly journals Giant nonlinear damping in nanoscale ferromagnets

2019 ◽  
Vol 5 (10) ◽  
pp. eaav6943 ◽  
Author(s):  
I. Barsukov ◽  
H. K. Lee ◽  
A. A. Jara ◽  
Y.-J. Chen ◽  
A. M. Gonçalves ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
High Resolution ◽  
Nonlinear Damping ◽  
Spin Torque ◽  
Magnetic Dynamics ◽  
Magnetic Damping ◽  
Microwave Magnetic Field ◽  
Geometric Confinement ◽  
Phenomenological Constant

Magnetic damping is a key metric for emerging technologies based on magnetic nanoparticles, such as spin torque memory and high-resolution biomagnetic imaging. Despite its importance, understanding of magnetic dissipation in nanoscale ferromagnets remains elusive, and the damping is often treated as a phenomenological constant. Here, we report the discovery of a giant frequency-dependent nonlinear damping that strongly alters the response of a nanoscale ferromagnet to spin torque and microwave magnetic field. This damping mechanism originates from three-magnon scattering that is strongly enhanced by geometric confinement of magnons in the nanomagnet. We show that the giant nonlinear damping can invert the effect of spin torque on a nanomagnet, leading to an unexpected current-induced enhancement of damping by an antidamping torque. Our work advances the understanding of magnetic dynamics in nanoscale ferromagnets and spin torque devices.

scholarly journals Microwave magnetic field modulation of spin torque oscillator based on perpendicular magnetic tunnel junctions

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Witold Skowroński ◽  
Jakub Chęciński ◽  
Sławomir Ziętek ◽  
Kay Yakushiji ◽  
Shinji Yuasa
Keyword(s):  
Magnetic Field ◽  
Microwave Field ◽  
Magnetic Tunnel Junction ◽  
Communication Technologies ◽  
Field Application ◽  
Spin Torque ◽  
Inductive Loop ◽  
High Data ◽  
Microwave Magnetic Field ◽  
Field Modulation

AbstractModulation of a microwave signal generated by the spin-torque oscillator (STO) based on a magnetic tunnel junction (MTJ) with perpendicularly magnetized free layer is investigated. Magnetic field inductive loop was created during MTJ fabrication process, which enables microwave field application during STO operation. The frequency modulation by the microwave magnetic field of up to 3 GHz is explored, showing a potential for application in high-data-rate communication technologies. Moreover, an inductive loop is used for self-synchronization of the STO signal, which after field-locking, exhibits significant improvement of the linewidth and oscillation power.

Switching field reduction of a perpendicular magnetic nanodot in a microwave magnetic field emitted from a spin-torque oscillator

2017 ◽  
Vol 110 (13) ◽  
pp. 132403 ◽  
Author(s):  
Hirofumi Suto ◽  
Taro Kanao ◽  
Tazumi Nagasawa ◽  
Kiwamu Kudo ◽  
Koichi Mizushima ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Spin Torque ◽  
Switching Field ◽  
Microwave Magnetic Field

Analysis method of a spin-torque oscillator using dc resistance change during injection locking to an external microwave magnetic field

2021 ◽  
Vol 119 (14) ◽  
pp. 142405
Author(s):  
Nagarjuna Asam ◽  
Hirofumi Suto ◽  
Shingo Tamaru ◽  
Hossein Sepehri-Amin ◽  
Anton Bolyachkin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Injection Locking ◽  
Spin Torque ◽  
Analysis Method ◽  
Resistance Change ◽  
Microwave Magnetic Field ◽  
Dc Resistance

Analysis of an all-in-plane spin-torque oscillator using injection locking to an external microwave magnetic field

2021 ◽  
Author(s):  
Hirofumi Suto ◽  
Hossein Sepehri-Amin ◽  
Nagarjuna Asam ◽  
Weinan Zhou ◽  
Anton Bolyachkin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Injection Locking ◽  
Spin Torque ◽  
Microwave Magnetic Field

Imaging of ferroelectric domain walls by electron holography

1992 ◽  
Vol 50 (1) ◽  
pp. 246-247
Author(s):  
Xiao Zhang
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Domain Walls ◽  
Ferroelectric Domain ◽  
Object Wave ◽  
Electron Holography ◽  
High Resolution Imaging ◽  
Quantitative Measurements ◽  
Resolution Imaging ◽  
Electron Microscopes

Electron holography has recently been available to modern electron microscopy labs with the development of field emission electron microscopes. The unique advantage of recording both amplitude and phase of the object wave makes electron holography a effective tool to study electron optical phase objects. The visibility of the phase shifts of the object wave makes it possible to directly image the distributions of an electric or a magnetic field at high resolution. This work presents preliminary results of first high resolution imaging of ferroelectric domain walls by electron holography in BaTiO3 and quantitative measurements of electrostatic field distribution across domain walls.

A Super-High-Resolution HVEM (H-1500) Newly Installed in NIRIM

1990 ◽  
Vol 48 (1) ◽  
pp. 142-143
Author(s):  
S. Horiuchi ◽  
Y. Matsui
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Chromatic Aberration ◽  
Inorganic Materials ◽  
Electron Gun ◽  
Resolving Power ◽  
National Budget ◽  
Voltage Electron ◽  
Specimen Holder ◽  
The Magnetic Field

A new high-voltage electron microscope (H-1500) specially aiming at super-high-resolution (1.0 Å point-to-point resolution) is now installed in National Institute for Research in Inorganic Materials ( NIRIM ), in collaboration with Hitachi Ltd. The national budget of about 1 billion yen including that for a new building has been spent for the construction in the last two years (1988-1989). Here we introduce some essential characteristics of the microscope.(1) According to the analysis on the magnetic field in an electron lens, based on the finite-element-method, the spherical as well as chromatic aberration coefficients ( Cs and Cc ). which enables us to reach the resolving power of 1.0Å. have been estimated as a function of the accelerating As a result of the calculaton. it was noted that more than 1250 kV is needed even when we apply the highest level of the technology and materials available at present. On the other hand, we must consider the protection against the leakage of X-ray. We have then decided to set the conventional accelerating voltage at 1300 kV. However. the maximum accessible voltage is 1500 kV, which is practically important to realize higher voltage stabillity. At 1300 kV it is expected that Cs= 1.7 mm and Cc=3.4 mm with the attachment of the specimen holder, which tilts bi-axially in an angle of 35° ( Fig.1 ). In order to minimize the value of Cc a small tank is additionally placed inside the generator tank, which must serve to seal the magnetic field around the acceleration tube. An electron gun with LaB6 tip is used.

High Resolution Current Imaging by Direct Magnetic Field Sensing

2003 ◽  
Author(s):  
S.I. Woods ◽  
Nesco M. Lettsome ◽  
A.B. Cawthorne ◽  
L.A. Knauss ◽  
R.H. Koch
Keyword(s):  
Magnetic Field ◽  
High Resolution ◽  
Spatial Resolution ◽  
Great Promise ◽  
Magnetoresistive Sensor ◽  
Magnetic Sensitivity ◽  
Current Lines ◽  
Scanning Squid ◽  
Scanning Fiber ◽  
Ferromagnetic Probe

Abstract Two types of magnetic microscopes have been investigated for use in high resolution current mapping. The scanning fiber/SQUID microscope uses a SQUID sensor coupled to a nanoscale ferromagnetic probe, and the GMR microscope employs a nanoscale giant magnetoresistive sensor. Initial scans demonstrate that these microscopes can resolve current lines less than 10 µm apart with edge resolution of 1 µm. These types of microscopes are compared with the performance of a standard scanning SQUID microscope and with each other with respect to spatial resolution and magnetic sensitivity. Both microscopes show great promise for identifying current defects in die level devices.

scholarly journals Manipulation of light transmission from stable magnetic microrods formed by the alignment of magnetic nanoparticles

RSC Advances ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 2390-2396
Author(s):  
Yoon Ji Seo ◽  
Hyung Gyu Lee ◽  
Jun Seok Yang ◽  
Hwanyeop Jeong ◽  
Jeonghun Han ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Light Transmission ◽  
Smart Window ◽  
Light Valve

Magnetic microrods were synthesised from magnetic nanoparticles by alignment using a magnetic field. The transparency difference was maximised and the anisotropic features of the rods were used as a light valve to control the transparency of a smart window.

scholarly journals Advantages and Disadvantages of Using Magnetic Nanoparticles for the Treatment of Complicated Ocular Disorders

Pharmaceutics ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1157
Author(s):  
Elena K. Schneider-Futschik ◽  
Felisa Reyes-Ortega
Keyword(s):  
Magnetic Field ◽  
Magnetic Nanoparticles ◽  
Therapeutic Efficacy ◽  
Genetic Diseases ◽  
Systemic Exposure ◽  
Drug Carriers ◽  
Three Dimensions ◽  
Target Point ◽  
Advantages And Disadvantages ◽  
Ocular Disorders

Nanomaterials provide enormous opportunities to overcome the limitations of conventional ocular delivery systems, such as low therapeutic efficacy, side effects due to the systemic exposure, or invasive surgery. Apart from the more common ocular disorders, there are some genetic diseases, such as cystic fibrosis, that develop ocular disorders as secondary effects as long as the disease progresses. These patients are more difficult to be pharmacologically treated using conventional drug routes (topically, systemic), since specific pharmacological formulations can be incompatible, display increased toxicity, or their therapeutic efficacy decreases with the administration of different kind of chemical molecules. Magnetic nanoparticles can be used as potent drug carriers and magnetic hyperthermia agents due to their response to an external magnetic field. Drugs can be concentrated in the target point, limiting the damage to other tissues. The other advantage of these magnetic nanoparticles is that they can act as magnetic resonance imaging agents, allowing the detection of the exact location of the disease. However, there are some drawbacks related to their use in drug delivery, such as the limitation to maintain efficacy in the target organ once the magnetic field is removed from outside. Another disadvantage is the difficulty in maintaining the therapeutic action in three dimensions inside the human body. This review summarizes all the application possibilities related to magnetic nanoparticles in ocular diseases.

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