65 research outputs found
Longitudinal relaxation and thermoactivation of quantum superparamagnets
The relaxation mechanisms of a quantum nanomagnet are discussed in the frame
of linear response theory. We use a spin Hamiltonian with a uniaxial potential
barrier plus a Zeeman term. The spin, having arbitrary , is coupled to a
bosonic environment. From the eigenstructure of the relaxation matrix, we
identify two main mechanisms, namely, thermal activation over the barrier, with
a time scale \eival_1^{-1}, and a faster dynamics inside the potential wells,
with characteristic time \eivalW^{-1}. This allows to introduce a simple
analytical formula for the response, which agrees well with the exact numerical
results, and cover experiments even under moderate to strong fields in the
superparamagnetic range. In passing, we generalize known classical results for
a number of quantities (e.g., integral relaxation times, initial decay time,
Kramers rate), results that are recovered in the limit .Comment: submitted to Phys. Rev.
Thermophysics of metal alkanoates II. Heat capacities and thermodynamic properties of sodium propanoate
The heat capacity of sodium propanoate has been measured from 9 to 580 K by adiabatic calorimetry and considerable metastability noted between 60 and 215 K. Values at 298.15 K of Cp,m/R, Smo/R, "Hmo-Hmo(0)'/R, and "Gmo-Hmo(0)'/RT are 16.16, 18.29, 2809.1 K, and -8.872. Comparisons with d.s.c. results and other reported phase behavior are provided.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/25432/1/0000882.pd
Study on the equilibrium in the MCl2?CH3OH?H2O System (M = Sr2+, Ba2+) at 25�C and 50�C
Inertial effects in the orientational relaxation of rodlike molecules in a uniaxial potential
The conode position at equilibrium between solid and liquid phases in a three-component system with unlimited mutual component solubility in both phases
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