A Heisenberg Ferromagnet With Biquadratic and Dipol-octupol Interactions

1981 ◽  
Vol 36 (8) ◽  
pp. 797-801 ◽  
Author(s):  
Z. Ba̮k
Keyword(s):  
Free Energy ◽  
Ground State ◽  
Collective Excitation ◽  
Field Approximation ◽  
Molecular Field ◽  
Heisenberg Ferromagnet ◽  
Excitation Spectra ◽  
Molecular Field Approximation ◽  
Biquadratic Exchange ◽  
Ferromagnetic Ground State

Abstract A Heisenberg S - 3/2 ferromagnet with isotropic biquadratic exchange and dipole-octupol coupling is discussed. The conditions for the exact ferromagnetic ground state are derived. The thermodynamical behaviour in the molecular field approximation is discussed. Collective excitation spectra and the 1/z correction to the free energy are found.

Effect of Biquadratic Exchange on Two Magnon States of Heisenberg Ferromagnets: Other Neighbor Exchange

1975 ◽  
Vol 53 (6) ◽  
pp. 637-647 ◽  
Author(s):  
D. A. Pink ◽  
Vijay Sachdeva
Keyword(s):  
Ground State ◽  
Nearest Neighbor ◽  
Ferromagnetic State ◽  
Localized States ◽  
Heisenberg Ferromagnet ◽  
Green Functions ◽  
Localized Modes ◽  
One Dimensional ◽  
Localized State ◽  
Biquadratic Exchange

We have investigated the two magnon localized states of a one dimensional Heisenberg ferromagnet the Hamiltonian of which is made up of nearest neighbor and next nearest neighbor isotropic bilinear and biquadratic exchange terms, and a single ion anisotropy term. We have restricted our choice of parameters so that the ground state at T = 0 is the fully aligned ferromagnetic state and we have used the thermodynamic Green functions where the averages have been evaluated in the ground state so that our results are good for [Formula: see text]. We have evaluated the probabilities of finding two spin deviations a distance n apart when the system is in a localized state described by total wave vector q. We have (a) compared the effects of ferromagnetic and antiferromagnetic next nearest neighbor exchange, (b) found that localized modes can lie below or above the two free magnon band depending upon the sign and magnitude of the biquadratic exchange, (c) found that in certain cases two spin deviations appear to behave like objects interacting only via a soft core, and (d) found that modes can have a large single ion component when the single ion anisotropy is zero.

GROUND STATE AND LOW-EXCITED STATES OF A BOSE GAS IN A FINITE ANISOTROPIC TRAP

2008 ◽  
Vol 22 (28) ◽  
pp. 5003-5014 ◽  
Author(s):  
LIANGHUI WEN ◽  
YONG-LI MA
Keyword(s):  
Ground State ◽  
Collective Excitation ◽  
Three Dimensional ◽  
Finite Amplitude ◽  
Einstein Condensate ◽  
Harmonic Potential ◽  
Excitation Spectra ◽  
Basis Expansion ◽  
Ground State Wavefunction ◽  
Bose Einstein Condensate

The motivation in this paper is to simulate numerically some properties of an interacting Bose–Einstein condensate at zero temperature in an axial symmetry trapping potential with finite amplitude for modeling the practical experimental cases. By use of the basis expansion using three-dimensional harmonic oscillator eigenfunctions, we obtain the ground-state wavefunction and the collective excitation spectra of the system in both usual harmonic potential and different amplitudes of the finite potential. After comparing our results for the finite potential with the data derived from the harmonic potential, we conclude that the finite trap in the practical experiments decreases the entire excitation frequencies in the whole regimes. This decrease is consistent with our analytic prediction qualitatively and agrees well with the experimental data quantitatively.

Calculation of the temperature induction coefficient of nanostructured hard magnetic Pr-Dy-Gd-Fe-Co-B materials using the molecular-field approximation

2010 ◽  
Vol 2010 (1) ◽  
pp. 53-56 ◽  
Author(s):  
V. P. Piskorskii ◽  
G. S. Burkhanov ◽  
O. G. Ospennikova ◽  
R. A. Valeev ◽  
I. S. Tereshina ◽  
...  
Keyword(s):  
Field Approximation ◽  
Molecular Field ◽  
Molecular Field Approximation ◽  
Temperature Induction
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