scholarly journals The magnetic properties of bismuth, III. Further measurements on the de Haas-van Alphen effect

1939 ◽  
Vol 170 (942) ◽  
pp. 341-364 ◽  
Keyword(s):  
Low Temperatures ◽  
Detailed Comparison ◽  
Analytical Form ◽  
Inhomogeneous Field ◽  
Cubic Lattice ◽  
Low Field ◽  
Faraday Method ◽  
The Magnetic Field ◽  
Simple Analytical Form ◽  
Field Strengths

As was'first shown by de Haas and van Alphen (1932), the susceptibility of bismuth single crystals at low temperatures depends in a peculiar periodic fashion on the magnetic field, and later this effect was studied in greater detail by Shoenberg and Zaki Uddin (1936), especially as regards the influence of temperature and impurities. The general features of the effect were found to agree qualitatively with Peierls’ theory (Peierls 1933), but since this theory was for a cubic lattice it could take no account of the directional features of the effect, and no detailed comparison could be made between the theory and the experiments. Since then, however, the theory has been developed by taking into account the actual crystal symmetry of bismuth (Blackman 1938; Landau 1938), and Landau has shown that the theory assumes a relatively simple analytical form at low field strengths, thus making desirable measurements at fields rather lower than those used in the previous experiments. With the ordinary Faraday method, it is not easy to make accurate susceptibility measurements at field strengths below about 4000 gauss, and this indeed was roughly the lowest field used in the previous work, but an even more serious disadvantage of this method is that it necessarily involves the crystal being in an inhomogeneous field, with the result that the measured susceptibility is always an average over an appreciable range of fields.

scholarly journals Anomalous Temperature and Field Behaviors of Magnetization in Cubic Lattice Frustrated Ferromagnets

2015 ◽  
Vol 233-234 ◽  
pp. 3-7
Author(s):  
A.N. Ignatenko ◽  
Andrey A. Katanin ◽  
Valentin Yu. Irkhin
Keyword(s):  
Experimental Data ◽  
Monte Carlo Simulation ◽  
Low Temperatures ◽  
Strong Field ◽  
Wave Spectrum ◽  
Exchange Interactions ◽  
Thermal Fluctuations ◽  
Anomalous Temperature ◽  
Cubic Lattice ◽  
Spin Wave Spectrum

Thermodynamic properties of cubic Heisenberg ferromagnets with competing exchange interactions are considered near the frustration point where the coefficient D in the spin-wave spectrum Ek ~ Dk2vanishes. Within the Dyson-Maleev formalism it is found that at low temperatures thermal fluctuations stabilize ferromagnetism by increasing the value of D. For not too strong frustration this leads to an unusual "concave" shape of the temperature dependence of magnetization, which is in agreement with experimental data on the europium chalcogenides. Anomalous temperature behavior of magnetization is confirmed by Monte Carlo simulation. Strong field dependence of magnetization (paraprocess) at finite temperature is found near the frustration point.

Characteristics of Magnetic Resonance Sequences Used for Imaging Silicone Gel, Saline, and Gel-Saline Implants at Low Field Strengths

1994 ◽  
Vol 29 (8) ◽  
pp. 781-786 ◽  
Author(s):  
STEVEN FRANKEL ◽  
KATHRYN OCCHIPINTI ◽  
LEON KAUFMAN ◽  
DAVID KRAMER ◽  
JOSEPH CARLSON ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Silicone Gel ◽  
Low Field ◽  
Field Strengths

Integrated Magnetic Sensing of Electrostatically Actuated Thin-Film Microbridges

2002 ◽  
Vol 729 ◽  
Author(s):  
J. Gaspar ◽  
Haohua Li ◽  
P.P. Freitas ◽  
V. Chu ◽  
J.P. Conde
Keyword(s):  
Thin Film ◽  
Low Temperatures ◽  
Counter Electrode ◽  
Spin Valve ◽  
Metal Gate ◽  
Electrostatically Actuated ◽  
Glass Substrates ◽  
Hydrogenated Amorphous ◽  
Bridge Length ◽  
The Magnetic Field

AbstractBilayer microbridges of aluminum and hydrogenated amorphous silicon are fabricated using thin film technology and surface micromachining at low temperatures on glass substrates. The microstructure is electrostatically actuated by applying a voltage between the bridge and a metal gate counter electrode placed beneath it. The movement is measured with a precision close to 0.1 Å by sensing the magnetic field of a permanent magnet, deposited and patterned on top of the microbridge, with an integrated spin valve magnetic sensor. The deflection of the bridge is at the same time monitored using an optical setup. The deflection of the structures is studied as a function of the driving applied gate voltage and bridge length and experimental results are analyzed with an electromechanical model.

scholarly journals Convective differential rotation in stars and planets – I. Theory

2020 ◽  
Vol 498 (3) ◽  
pp. 3758-3781 ◽  
Author(s):  
Adam S Jermyn ◽  
Shashikumar M Chitre ◽  
Pierre Lesaffre ◽  
Christopher A Tout
Keyword(s):  
Differential Rotation ◽  
Detailed Comparison ◽  
Companion Paper ◽  
Angular Frequency ◽  
Circulation Rate ◽  
Rotation Rates ◽  
Rotating Systems ◽  
Order Of Magnitude ◽  
The Magnetic Field ◽  
Hydrodynamic Systems

ABSTRACT We derive the scaling of differential rotation in both slowly and rapidly rotating convection zones using order of magnitude methods. Our calculations apply across stars and fluid planets and all rotation rates, as well as to both magnetized and purely hydrodynamic systems. We find shear |R∇Ω| of order the angular frequency Ω for slowly rotating systems with Ω ≪ |N|, where N is the Brünt–Väisälä frequency, and find that it declines as a power law in Ω for rapidly rotating systems with Ω ≫ |N|. We further calculate the meridional circulation rate and baroclinicity and examine the magnetic field strength in the rapidly rotating limit. Our results are in general agreement with simulations and observations and we perform a detailed comparison with those in a companion paper.

Differential Drive Servo Valve Based on MSMA

2012 ◽  
Vol 271-272 ◽  
pp. 858-862
Author(s):  
Chao Yu ◽  
Kui Sheng Chen ◽  
Shu Guang Fu
Keyword(s):  
Simulation Analysis ◽  
Structural Features ◽  
Paper Briefly ◽  
Servo Valve ◽  
Differential Drive ◽  
High Frequency Response ◽  
Low Field ◽  
Working Principle ◽  
Large Flow ◽  
The Magnetic Field

Aimed at the contradiction between high frequency response and large flow of servo valve, the paper puts forward a 2D servo valve with differential drive based on magnetic controlled shape memory alloy(MSMA). To realize large flow control, the valve-spool is set of flow increasing orifice to match the flow increasing window on the valve-sleeve. The paper briefly introduces the structural features of the 2D servo valve and the working principle of the differential drive. It also has a simulation analysis on the magnetic field of the drive and the low field of the valve. Simulation results show that, the flow of the valve is linear with the input current.

scholarly journals Magnetic Field Strengths of Spiral Galaxies and the Far-Infrared/Radio Correlation

1990 ◽  
Vol 140 ◽  
pp. 241-241
Author(s):  
A. J. Fitt ◽  
P. Alexander
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Field Distribution ◽  
Detection Rate ◽  
Spiral Galaxies ◽  
Far Infrared ◽  
Magnetic Field Distribution ◽  
Selection Effects ◽  
The Magnetic Field ◽  
Field Strengths

We have calculated equipartition magnetic fields for a complete, optically-selected sample of 165 spiral galaxies. The magnetic field distribution (fig. 1) is type independent, and shows remarkably little spread in values, around 1 decade in B. This is not due to selection effects because of the nature of the sample and the 95 percent detection rate.

scholarly journals Detection of cerebral lactate in vivo during hypoxemia by 1H NMR at relatively low field strengths (1.9 T).

1984 ◽  
Vol 81 (8) ◽  
pp. 2517-2519 ◽  
Author(s):  
K. L. Behar ◽  
D. L. Rothman ◽  
R. G. Shulman ◽  
O. A. Petroff ◽  
J. W. Prichard
Keyword(s):  
1H Nmr ◽  
Low Field ◽  
Field Strengths

scholarly journals A Simple Free Energy for the Isotropic-Nematic Phase Transition of Rods

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Remco Tuinier
Keyword(s):  
Free Energy ◽  
Nematic Phase ◽  
Analytical Form ◽  
Orientation Distribution ◽  
Scaled Particle Theory ◽  
Particle Theory ◽  
Aspect Ratios ◽  
Wide Range ◽  
Hard Rods ◽  
Simple Analytical Form

A free energy expression is proposed that describes the isotropic-nematic binodal concentrations of hard rods. A simple analytical form for this free energy was yet only available using a Gaussian trial function for the orientation distribution function (ODF), leading, however, to a significant deviation of the predicted binodals. The new free energy proposed here is based upon a rationalized correction to the orientational and packing entropies when using the Gaussian ODF. In combination with Parsons-Lee theory or scaled particle theory, it enables describing the isotropic-nematic phase coexistence concentrations of rods accurately using the simple Gaussian ODF for a wide range of aspect ratios.

scholarly journals Programmable shunt valve interactions with osseointegrated hearing devices

2017 ◽  
Vol 19 (4) ◽  
pp. 384-390
Author(s):  
Matthew J. Pierson ◽  
Daniel Wehrmann ◽  
J. Andrew Albers ◽  
Najib E. El Tecle ◽  
Dary Costa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Shunt Valve ◽  
Vp Shunt ◽  
Magnetic Attachment ◽  
Hearing Devices ◽  
Programmable Valves ◽  
The Magnetic Field ◽  
Field Strengths

OBJECTIVE Patients with ventriculoperitoneal (VP) shunts with programmable valves who would benefit from osseointegrated hearing devices (OIHDs) represent a unique population. The aim of this study was to evaluate the magnetic field strengths of 4 OIHDs and their interactions with 5 programmable VP shunt valves. METHODS Magnetic field strength was measured as a function of distance for each hearing device (Cochlear Baha 5, Cochlear Baha BP110, Oticon Ponto Plus Power, and Medtronic Sophono) in the following modes: inactive, active in quiet, and active in 60 decibels of background noise in the sound booth. The hearing devices were introduced to each shunt valve (Aesculap proGAV, Aesculap proGAV 2.0, Codman Hakim, Codman Certas, and Medtronic Strata II) also as a function of distance in these identical 3 settings. Each trial was repeated 5 times. Between each trial, the valves were assessed for a change in setting. Finally, using a skull model, the devices were introduced to each other in standard anatomical locations and the valves were assessed for a change in settings. RESULTS The maximum magnetic field strengths generated by the Cochlear Baha 5, BP110, and Oticon OIHDs were 1.1, 36.2, and 48.7 gauss (G), respectively. The maximum strength generated by the Sophono device was > 800 G. The magnetic field strength of the hearing devices decreased markedly with increasing distance from the device. The strength of the Sophono's magnetic attachment decreased to 34.8 G at 5 mm. The Codman Hakim, Codman Certas, and Medtronic Strata II valve settings changed when rotating the valves next to the Sophono abutment. No other changes in valve settings occurred in the distance or anatomical models for any other trials. CONCLUSIONS This is the first study evaluating the interaction between OIHDs and programmable VP shunt valves. The findings suggest that it is safe to use these devices together without having to switch to a nonprogrammable valve or move the shunt valve to a more distant location. Still, care should be taken if the Sophono device is used to ensure that the valve is ≥ 5 mm away from the magnetic attachment.

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