MAGNETIC SUSCEPTIBILITY OF A STRONGLY CORRELATED d–p MODEL

The d–p band model, a periodic array of strongly correlated d states with hopping to a p band, and in the presence of a uniform applied magnetic field is studied as a function of temperature using Roth's variational method. Expanding the σ spin electron occupation numbers of d and p states to first order in the magnetic field h, we calculate the linear term of the field induced magnetization and thus the susceptibility. This is given in terms of the number of holes for La 2 - x Sr x CuO 4, in the limit of strongd–d correlations and we study the role of doping x and temperature "T" on the susceptibility.

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The magnetic susceptibility of an electron gas

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1962.0005 ◽

1962 ◽

Vol 265 (1321) ◽

pp. 215-228 ◽

Cited By ~ 24

Keyword(s):

Magnetic Field ◽

Magnetic Susceptibility ◽

Electron Gas ◽

Quantum Mechanical ◽

Uniform Field ◽

Zero Temperature ◽

Coupling Constant ◽

First Order ◽

The Magnetic Field ◽

Density Expansion

The cluster expansion of the quantum-mechanical grand partition function is obtained for a gas of interacting charged particles in a uniform magnetic field. The magnetic field is conveniently included by using a Green function for a charged particle in a uniform field. The theory is applied to calculate the magnetic susceptibility of an electron gas for small magnetic fields. For Boltzmann statistics the equation of state is unaltered to the DebyeHuckel approximation and the field only enters into the quantum-mechanical corrections to this equation. The first terms in a low-density expansion of the susceptibility are obtained. For Fermi-Dirac statistics an exact high-density expansion of the susceptibility to first order in the coupling constant is obtained at zero temperature. The first-order exchange energy is divergent but this divergence is removed by including the ring diagrams.

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What Density of Magnetosheath Sodium Ions Can Provide the Observed Decrease in the Magnetic Field of the “Double Magnetopause” during the First MESSENGER Flyby?

Symmetry ◽

10.3390/sym13071168 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1168

Author(s):

Elena Belenkaya ◽

Ivan Pensionerov

Keyword(s):

Magnetic Field ◽

Analytical Approach ◽

Field Structure ◽

Sodium Ions ◽

Plasma Parameters ◽

Calculation Results ◽

Magnetizing Current ◽

The Magnetic Field ◽

Density Excess

On 14 January 2008, the MESSENGER spacecraft, during its first flyby around Mercury, recorded the magnetic field structure, which was later called the “double magnetopause”. The role of sodium ions penetrating into the Hermean magnetosphere from the magnetosheath in generation of this structure has been discussed since then. The violation of the symmetry of the plasma parameters at the magnetopause is the cause of the magnetizing current generation. Here, we consider whether the change in the density of sodium ions on both sides of the Hermean magnetopause could be the cause of a wide diamagnetic current in the magnetosphere at its dawn-side boundary observed during the first MESSENGER flyby. In the present paper, we propose an analytical approach that made it possible to determine the magnetosheath Na+ density excess providing the best agreement between the calculation results and the observed magnetic field in the double magnetopause.

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Connecting a Star’s Convection Zone with its Corona

Publications of the Astronomical Society of Australia ◽

10.1017/s1323358000020245 ◽

1995 ◽

Vol 12 (2) ◽

pp. 180-185 ◽

Cited By ~ 2

Author(s):

D. J. Galloway ◽

C. A. Jones

Keyword(s):

Magnetic Field ◽

Convection Zone ◽

Flux Rope ◽

Field System ◽

Stellar Convection ◽

Coronal Activity ◽

Flux Concentration ◽

Global Understanding ◽

The Magnetic Field

AbstractThis paper discusses problems which have as their uniting theme the need to understand the coupling between a stellar convection zone and a magnetically dominated corona above it. Interest is concentrated on how the convection drives the atmosphere above, loading it with the currents that give rise to flares and other forms of coronal activity. The role of boundary conditions appears to be crucial, suggesting that a global understanding of the magnetic field system is necessary to explain what is observed in the corona. Calculations are presented which suggest that currents flowing up a flux rope return not in the immediate vicinity of the rope but rather in an alternative flux concentration located some distance away.

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Doppler-Shifted Cyclotron Resonance in Thin Metal Films

Canadian Journal of Physics ◽

10.1139/p72-283 ◽

1972 ◽

Vol 50 (18) ◽

pp. 2122-2137

Author(s):

R. Turner ◽

J. F. Cochran

Keyword(s):

Magnetic Field ◽

Metal Films ◽

Thin Metal Film ◽

Thin Metal ◽

Free Electrons ◽

Fermi Surfaces ◽

First Order ◽

Simple Quantum ◽

The Magnetic Field ◽

Good Agreement

According to Van Gelder the microwave absorption by a thin metal film in the presence of a static magnetic field normal to the film contains a series of peaks as the magnetic field is varied. In the present paper it is argued that these peaks correspond to Doppler-shifted cyclotron resonances of the carriers in the metal due to the quantization of electron momenta normal to the plane of the film. A simple quantum calculation is presented for the case of free electrons where the film is thin enough that to first order the microwave fields within are determined only by the boundary conditions and Maxwell's equations. The quantum expression is in good agreement with the absorption calculated using semiclassical arguments which can be readily extended to more complicated Fermi surfaces.

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Reversibility of the Magnetocaloric Effect in the Bean-Rodbell Model

Magnetochemistry ◽

10.3390/magnetochemistry7050060 ◽

2021 ◽

Vol 7 (5) ◽

pp. 60

Author(s):

Luis M. Moreno-Ramírez ◽

Victorino Franco

Keyword(s):

Magnetic Field ◽

Thermal Hysteresis ◽

Entropy Change ◽

Second Order ◽

Zero Field ◽

First Order ◽

Magnetic Field Change ◽

Magnetocaloric Materials ◽

Moderate Magnetic Field ◽

The Magnetic Field

The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the η parameter (η<1 for second-order and η>1 for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (TEC), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of TEC is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with η≈1.3−1.8 have better TEC than those corresponding to stronger first-order transitions and even second-order ones.

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The role of slow magnetostrophic waves in dipole formation in rapidly rotating dynamos

10.5194/egusphere-egu21-15480 ◽

2021 ◽

Author(s):

Aditya Varma ◽

Binod Sreenivasan

Keyword(s):

Magnetic Field ◽

Threshold Value ◽

Dipole Field ◽

Wave Frequency ◽

Alfven Wave ◽

Inertial Waves ◽

Axial Dipole ◽

Wide Range ◽

The Magnetic Field

<p>It is known that the columnar structures in rapidly rotating convection are affected by the magnetic field in ways that enhance their helicity. This may explain the dominance of the axial dipole in rotating dynamos. Dynamo simulations starting from a small seed magnetic field have shown that the growth of the field is accompanied by the excitation of convection in the energy-containing length scales. Here, this process is studied by examining axial wave motions in the growth phase of the dynamo for a wide range of thermal forcing. In the early stages of evolution where the field is weak, fast inertial waves weakly modified by the magnetic field are abundantly present. As the field strength(measured by the ratio of the Alfven wave to the inertial wave frequency) exceeds a threshold value, slow magnetostrophic waves are spontaneously generated. The excitation of the slow waves coincides with the generation of helicity through columnar motion, and is followed by the formation of the axial dipole from a chaotic, multipolar state. In strongly driven convection, the slow wave frequency is attenuated, causing weakening of the axial dipole intensity. Kinematic dynamo simulations at the same parameters, where only fast inertial waves are present, fail to produce the axial dipole field. The dipole field in planetary dynamos may thus be supported by the helicity from slow magnetostrophic waves.</p>

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High magnetic field NMR investigation of the spin density wave phase of TMTSF2PF6

Journal de Physique IV (Proceedings) ◽

10.1051/jp4:20020445 ◽

2002 ◽

Vol 12 (9) ◽

pp. 389-389

Author(s):

W. G. Clark ◽

F. Zamborsky ◽

B. Alavi ◽

P. Vonlanthen ◽

W. Moulton ◽

...

Keyword(s):

Magnetic Field ◽

Spin Density ◽

Density Wave ◽

Spin Density Wave ◽

Proton Relaxation ◽

High Magnetic Fields ◽

Organic Conductor ◽

First Order ◽

The Magnetic Field ◽

Very High

We report proton NMR measurements of the effect of very high magnetic fields up to 44.7 T (1.9 GHz) on the spin density wave (SDW) transition of the organic conductor TMTSF2PF6. Up to 1.8 GHz, no effect of critical slowing close to the transition is seen on the proton relaxation rate (1/T1), which is determined by the SDW fluctuations associated with the phase transition at the NMR frequency. Thus, the correlation time for such fluctuations is less than $1O^{-10}$s. A possible explanation for the absence of longer correlation times is that the transition is weakly first order, so that the full critical divergence is never achieved. The measurements also show a dependence of the transition temperature on the orientation of the magnetic field and a quadratic dependence on its magnitude that agrees with earlier transport measurements at lower fields. The UCLA part of this work was supported by NSF Grant DMR-0072524.

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Chiral Magneto-Electrochemistry

Magnetochemistry ◽

10.3390/magnetochemistry4030036 ◽

2018 ◽

Vol 4 (3) ◽

pp. 36 ◽

Cited By ~ 5

Author(s):

Anup Kumar ◽

Prakash Mondal ◽

Claudio Fontanesi

Keyword(s):

Magnetic Field ◽

Experimental Studies ◽

Spin Accumulation ◽

Chiral Molecules ◽

Electrochemical System ◽

Ferromagnetic Electrodes ◽

Spin Polarized ◽

The Magnetic Field ◽

Research Domain

Magneto-electrochemistry (MEC) is a unique paradigm in science, where electrochemical experiments are carried out as a function of an applied magnetic field, creating a new horizon of potential scientific interest and technological applications. Over time, detailed understanding of this research domain was developed to identify and rationalize the possible effects exerted by a magnetic field on the various microscopic processes occurring in an electrochemical system. Notably, until a few years ago, the role of spin was not taken into account in the field of magneto-electrochemistry. Remarkably, recent experimental studies reveal that electron transmission through chiral molecules is spin selective and this effect has been referred to as the chiral-induced spin selectivity (CISS) effect. Spin-dependent electrochemistry originates from the implementation of the CISS effect in electrochemistry, where the magnetic field is used to obtain spin-polarized currents (using ferromagnetic electrodes) or, conversely, a magnetic field is obtained as the result of spin accumulation.

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