The thermal conductivity of Ni 2 + doped KMgF 3 in a magnetic field at low temperatures: the effect of single ions and coupled pairs

1970 ◽  
Vol 315 (1523) ◽  
pp. 551-568 ◽  
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Elastic Constants ◽  
Low Temperatures ◽  
Coupling Constants ◽  
Thermal Resistivity ◽  
Paramagnetic Resonance ◽  
Spin Lattice ◽  
Average Spin ◽  
Lattice Coupling

The thermal conductivity between 0.4 and 4.2 K and in magnetic fields up to 50 kOe of KMgF 3 doped with Ni 2+ has been measured. The results are analysed to give values of the average spin-lattice coupling constants ( x Sl ) for the Ni 2+ ion. These are in agreement with values calculated using the magneto-elastic constants (GX1 and 6r44) derived from acoustic paramagnetic resonance (a.p.r.) experiments. Below IK the thermal resistivity as a function of magnetic field shows a number of anomalies, for which possible causes are discussed; it is concluded that they result from phonon interactions with exchange-coupled pairs of Ni 2+ ions. Such pairs are also observed in a.p.r. experiments.

The effect of a magnetic field on the thermal conductivity of paramagnetic crystals: cerium ethylsulphate

1968 ◽  
Vol 302 (1470) ◽  
pp. 419-436 ◽  
Keyword(s):  
Magnetic Field ◽  
Thermal Conductivity ◽  
Energy Levels ◽  
Thermal Resistivity ◽  
Zero Field ◽  
Coupling Constant ◽  
Spin Lattice ◽  
Spin Interactions ◽  
The Mean ◽  
The Magnetic Field

The thermal conductivity of crystals of concentrated cerium ethylsulphate has been measured in the range 1 to 4·58°K and in magnetic fields of up to 53 kG. In zero field there is a marked anomaly at 2·5°K in the variation of conductivity with temperature. Owing to the anisotropy of the g -values the magnetic field dependence of the thermal resistivity at constant temperature depends on the field direction; with the field parallel to the hexagonal axis, a maximum occurs in the resistivity which moves roughly linearly with temperature, and in very high fields it is always less than in zero field; with the field applied in the perpendicular direction a resistivity maximum is only observed above 2°K, and in the highest available field it is always much greater than in zero field. These results are explained by assuming that direct process phonon-spin interactions scatter certain bands of phonons whose frequency depends on the separation of the energy levels produced by the applied magnetic field. A statistical theory is used to determine the relative populations of the energy levels in the calculation of the thermal resistivity. It is assumed that the spin-phonon absorption lineshape is Gaussian. By fitting the theory to the experimental data, approximate values of the spin-lattice coupling constant, the linewidth of the transitions and the mean free paths for boundary and point-defect scattering are obtained.

Giant effect of spin–lattice coupling on the thermal transport in two-dimensional ferromagnetic CrI3

2020 ◽  
Vol 8 (10) ◽  
pp. 3520-3526 ◽  
Author(s):  
Guangzhao Qin ◽  
Huimin Wang ◽  
Lichuan Zhang ◽  
Zhenzhen Qin ◽  
Ming Hu
Keyword(s):  
Thermal Conductivity ◽  
Thermal Transport ◽  
Magnetic Storage ◽  
Two Dimensional ◽  
Spin Lattice ◽  
Lattice Coupling

The thermal conductivity of monolayer CrI3 is enlarged more than two orders of magnitude by the spin–lattice coupling, which would be large enough for its applications in nanoelectronics and magnetic storage.

The Electron Paramagnetic Resonance Spectrum of γ-Irradiated Dimethyl Malonic Acid

2004 ◽  
Vol 59 (1-2) ◽  
pp. 103-104 ◽  
Author(s):  
Biray Aşik ◽  
Mehmet Birey
Keyword(s):  
Magnetic Field ◽  
Electron Paramagnetic Resonance ◽  
Electron Paramagnetic Resonance Spectrum ◽  
Single Crystals ◽  
Malonic Acid ◽  
Hyperfine Coupling ◽  
Resonance Spectrum ◽  
Coupling Constants ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

The electron paramagnetic resonance of γ -Irradiated single crystals of dimethyl malonic acid [(CH3)2C(COOH)2] has been studied for different orientations of the crystal in a magnetic field. The radicals produced by gamma irradiation have been investigated between 123 and 300 K. The spectra were found to be temperature independent, and radiation damage centres were attributed to [(CH3)2C(COOH)2]+ radicals. The g factor and hyperfine coupling constants were found to be almost isotropic with average values g = 2.0036, a(COOH)2 = 0.5 mT, a(CH3)2 = 2.1 mT, respectively, and spin density ρ = 91% of the [(CH3)2C(COOH)2]+ radical.

scholarly journals Die kinetischen Konstanten des Triplett-Zustandes von Fluoren-Molekülen / The Cinetic Constants of the Triplet Stale of Fluorene Molecules

1972 ◽  
Vol 27 (2) ◽  
pp. 198-209
Author(s):  
H. Sixl ◽  
H. Wolf
Keyword(s):  
Magnetic Field ◽  
Decay Time ◽  
Radiative Decay ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Average Spin ◽  
Optically Detected ◽  
Metastable Triplet State ◽  
Relaxation Rate Constant

AbstractThe metastable triplet state T1 of fluorene molecules in a fluorene crystal, disturbed by the presence of dibenzothiophene (“X-traps”) was investigated at 1.6 and 4.2 °K. From ESR measurements a model for the fluoren X-traps is derived. The X-trap molecule is misoriented by an angle of 2,5° in the fluorene crystal.The rate constants for population (s), radiative decay (kD) and total decay (k) of the three magnetic sublevels of T1 were determined by analysis of phosphorescence intensity and decay time in high magnetic field and by optically detected ESR. We find (with z = axis perpendicular to the molecule, x = long axis): The average spin lattice relaxation rate constant is w = (0.8 ± 0.2) sec- 1 .

THEORY OF THE SPIN-LATTICE INTERACTION IN PARAMAGNETIC SALTS OF IRON-GROUP IONS

1966 ◽  
Vol 44 (7) ◽  
pp. 1613-1630 ◽  
Author(s):  
J. Van Kranendonk ◽  
Y. Y. Lee
Keyword(s):  
Coupling Constants ◽  
Subsequent Paper ◽  
Iron Group ◽  
Spin Variable ◽  
Effective Spin ◽  
General Symmetry ◽  
Spin Lattice ◽  
Lattice Coupling ◽  
Radiation Processes

The form of the spin-lattice coupling in hydrated salts of the iron-group ions is derived in terms of the lattice vibrational coordinates and the effective spin variable, using general symmetry arguments. The most important coupling terms for octahedral and spherical symmetry are given, and the role of the breathing and rotational modes is discussed, as well as the concept of adiabatic and non-adiabatic coupling. This work forms the basis of the semiclassical theory of phonon radiation processes and phonon multipole fields and interactions to be presented in a subsequent paper. Finally, explicit expressions for the coupling constants in terms of the electronic structure of the ions are also derived, for the case of a nondegenerate ground orbital level.

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