Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 2 of 2
Full-Text Articles in Physical Sciences and Mathematics
Solid State Phase Transitions Characterized By Esr And Xas, Juana Vivó Acrivos
Solid State Phase Transitions Characterized By Esr And Xas, Juana Vivó Acrivos
Juana Vivó Acrivos
Measurements of the relaxation time, of electron systems to a disturbance, by two different spectroscopic methods are examined in detail, with the purpose to establish how the presence of fluctuations near a solid state phase transition are made evident in insulators, conductors and superconductors. The absolute temperature and the relaxation time determine the thermodynamic stability of the electronic system near a phase transition by the Uncertainty Principle. At a given temperature T, Landau and Lifshitz obtain the stability from the lower limit of the uncertainty in entropy in units of the Boltzmann constant, S/kB << 1 when T >> 3.82 K ps. Magnetic resonance …
Esr Study Of Optically Induced Phase Transitions, Juana Vivó Acrivos, H. P. Hughes, S. S.P. Parkin
Esr Study Of Optically Induced Phase Transitions, Juana Vivó Acrivos, H. P. Hughes, S. S.P. Parkin
Juana Vivó Acrivos
We have identified an optically enhanced magnetic phase transition in the newly synthesized organic molecular charge transfer salt, (BEDT-TTF)3Ta2F11 (BEDT-TTF bisethylenedithiolotetrathiafulvalene) by ESR absorption measurements in the X band microwave region. At room temperature, only a doublet state ESR absorption is observed, but below 30 K severa~ tripl~t E.SR absorpti_ons appear. The orientation dependence of the ESR absorption under lllummat10n at energies near the band gaps in the material ( 640 nm, T = 12 to 5 K H0 < 0.34 T) indicates that there are rapid spin exchange processes with times r < w-s; near 7 ~o 5 K.along cert~in ~rystallographic directions with a temperature dependen~e suggesting spm-lattlce relaxation times which proceed via Van Vleck "direct processes." This, to our knowledge, is the first case where the magnetic properties of a charge transfer salt are altered by the interaction with photons of energy equal to the band gaps in a low dimensional solid providing a new, interesting way to investigate these materials.