Two-Dimensional Melting of Magnetic Bubble Arrays: A Continuous Hexatic-To-Liquid Transition

1991 ◽  
Vol 248 ◽  
Author(s):  
R. Seshadri ◽  
R. M. Westervelt
Keyword(s):  
Magnetic Field ◽  
Imaging Techniques ◽  
Topological Defects ◽  
Gradient Field ◽  
Uniform Field ◽  
Two Dimensional ◽  
Bias Magnetic Field ◽  
Liquid Transition ◽  
Bubble Density ◽  
Dc Bias

AbstractArrays of two-dimensional magnetic bubbles in thin garnet films undergo a hexatic-toliquid transition as a function of bubble density controlled by an applied spatially uniform dc bias magnetic field that opposes the magnetization in the bubbles. The phase transition is driven by topological point defects. The bubbles are observed directly using optical microscopy and digital imaging techniques. In the presence of a linear gradient in the dc bias magnetic field the hexatic-to-liquid transition occurs spatially in the direction of the gradient. As the system goes from hexatic to liquid, a continuous decrease in bubble density accompanied by a continuous disordering of the array is observed along the gradient direction. This continuous disordering persists even after the system is allowed to equilibrate for very long periods of time, indicating that the hexatic-to-liquid transition is continuous at equilibrium. Dynamics of topological defects observed in the gradient field correspond to those observed in the uniform field.

scholarly journals Particle Acceleration in Collisionless Magnetic Reconnection

2001 ◽  
Vol 203 ◽  
pp. 555-557
Author(s):  
P. K. Browning ◽  
G. E. Vekstein
Keyword(s):  
Magnetic Field ◽  
Field Component ◽  
Charged Particles ◽  
Energy Spectra ◽  
Uniform Field ◽  
Two Dimensional ◽  
Point Field ◽  
Field Geometry ◽  
Collisionless Reconnection ◽  
Accelerated Particles

We investigate the acceleration of charged particles in the framework of collisionless reconnection. A steady reconnection scenario is considered, with a two dimensional X-point magnetic field geometry having also a uniform field component transverse to the plane of the X-point field, and an inductive electric field generating an inflow of particles. Test particle trajectories are studied, and the energy spectra of the accelerated particles are determined.

Magnetoelectric anisotropy in laminate composite for detecting magnetic field

2019 ◽  
Vol 12 (01) ◽  
pp. 1850098 ◽  
Author(s):  
Li Lv ◽  
Xi Yao ◽  
Lin Gan ◽  
Xiaoli Zhang ◽  
Jian-Ping Zhou
Keyword(s):  
Magnetic Field ◽  
Phase Shift ◽  
Laminate Composite ◽  
Magnetoelectric Effect ◽  
Bias Magnetic Field ◽  
Magnetic Signal ◽  
Two Phase ◽  
Ac Magnetic Field ◽  
Dc Bias ◽  
Magnetoelectric Coefficient

Magnetoelectric anisotropy was researched in a disc laminate composite. The magnetoelectric coefficient exhibits a cosine characteristic with the angle between the direction of dc bias magnetic field [Formula: see text] and small ac sine magnetic signal [Formula: see text], no matter how [Formula: see text] rotates. Correspondingly, there are only two values of phase shift when the angle varies from 0 to 360[Formula: see text]. These two phase shifts only depend on [Formula: see text] mapping on [Formula: see text], i.e., sign of dot product of [Formula: see text] and [Formula: see text] [Sgn([Formula: see text])], implying that [Formula: see text]cos[Formula: see text] produces charge through the magnetoelectric effect. Then, a simple device was proposed to detect the magnitude and direction of ac magnetic field.

scholarly journals Alternating current magnetic susceptibility of a ferronematic

2017 ◽  
Vol 8 ◽  
pp. 2515-2520 ◽  
Author(s):  
Natália Tomašovičová ◽  
Jozef Kováč ◽  
Veronika Gdovinová ◽  
Nándor Éber ◽  
Tibor Tóth-Katona ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Susceptibility ◽  
Soft Matter ◽  
Experimental Studies ◽  
Bias Field ◽  
Information Storage ◽  
Isotropic Phase ◽  
Ac Magnetic Susceptibility ◽  
Bias Magnetic Field ◽  
Dc Bias

We report on experimental studies focusing on the dynamic ac magnetic susceptibility of a ferronematic. It has been shown recently, that in the isotropic phase of a ferronematic, a weak dc bias magnetic field of a few oersteds increases the ac magnetic susceptibility. This increment vanishes irreversibly if the substance is cooled down to the nematic phase, but can be reinduced by applying the dc bias field again in the isotropic phase [Tomašovičová, N. et al. Soft Matter 2016, 12, 5780–5786]. The effect has no analogue in the neat host liquid crystal. Here, we demonstrate that by doubling the concentration of the magnetic nanoparticles, the range of the dc bias magnetic field to which the ferronematic is sensitive without saturation can be increased by about two orders of magnitude. This finding paves a way to application possibilities, such as low magnetic field sensors, or basic logical elements for information storage.

scholarly journals Magnetoelectric effect in a Terfenol-D and electret capacitor system

2018 ◽  
Vol 238 ◽  
pp. 01004
Author(s):  
Tian-Xiang Gao ◽  
Yan-Wei Zhou ◽  
Su-Su Wang ◽  
Yun Zhou
Keyword(s):  
Magnetic Field ◽  
Magnetoelectric Effect ◽  
Hysteresis Loops ◽  
Dynamic Measurement ◽  
Test Period ◽  
Bias Magnetic Field ◽  
Magnetoelectric Sensors ◽  
Potential Applications ◽  
Dc Bias

A capacitor system based on a Terfenol-D rod and an electret film has been proposed. We used the traditional dynamic measurement to investigate the magnetoelectric effect of the system at the frequency of 50 kHz. The results show that the ME coefficient of the system is significantly affected by the DC bias magnetic field. The maximum tunability of the magnetoelectric effect based on the DC bias magnetic field is more than 10%. The induced AC voltage of effective values increases almost lineally with increasing AC signal magnetic field. The detected magnetoelectric effect of the system exhibits hysteresis, and the magnetoelectric hysteresis loops are almost unchanged with the test period. These findings provide a type of capacitor for potential applications in magnetic detections and magnetoelectric sensors.

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