Magnetic field thermodynamics

The basic problem of statistical mechanics is to evaluate the sum-over-states in equation 7.2 and obtain Z and F as functions of T and any other variables (such as external magnetic fields) that might appear in %. Any thermodynamic observable of interest can then be obtained in a straightforward manner from equation 7.5. In practice, however, the sum-over-states often turns out to be prohibitively difficult to evaluate. Instead, the physical system is usually replaced with a simpler model system and/or some simplifying approximations are made so that the sum-over-states can be evaluated directly. 

See W. F. Giauque and D. P. MacDougall, "Experiments Establishing the Thermodynamic Temperature Scale below 1 =K. The Magnetic and Thermodynamic Properties of Gadolinium Phosphomolybdate as a Function of Field and Temperature". J. Am. Chem. Soc., 60, 376-388 (1938). 

Generally, for a pure substance in which the composition is constant, only two of the thermodynamic quantities listed above need be specified as independent variables to uniquely define the system. In the presence of significant gravitational, electric, or magnetic fields, or where the surface area or chemical composition of the system is variable, additional quantities may be needed to fix the state of the system. We will limit our discussion to situations where these additional variables are held constant, and hence, do not need to be considered. 

Figure 4.1 Schematic diagram showing the thermodynamics of the demagnetization process. By changing the magnetic field from the initial value Hl to the final one Hf, with Hf < Hj a gain in magnetic entropy, ASm, occurs during the isothermal process from...

The term parametric pumping was coined by Wilhelm et al. [Wilhelm, Rice, and Bendelius, Ind. Eng. Chem. Fundam., 5,141-144 (1966)] to describe a liquid-phase adsorption process in which separation is achieved by periodically reversing not only flow but also an intensive thermodynamic property such as temperature, which influences adsorptivity. Moreover, they considered the concurrent cycling of pressure, pH, and electrical and magnetic fields. A lot of research and development has been conducted on thermal, pressure, and pH driven cycles, but to date only gas-phase pressure-swing parametric pumping has found much commercial acceptance. 

Thermodynamic calculations, 14 86t Thermodynamic critical magnetic fields, 23 809-811... 

Thermodynamic Consequences of Multiple States Changes in Phase Equilibria Directly Attributable to Interaction with External Magnetic Fields... 

The contradictions that arise in the thermodynamics of a photon gas, and that are likely to be clarified by having a longitudinal magnetic field part... 

Figure 13.16 Magnetization verses applied magnetic field for (a) a type I superconductor and (b) a type II superconductor. For the type I superconductor, the magnetic flux does not penetrate the sample below 9 Cc where the sample is a superconductor. Above rMc, the sample is a normal conductor. For the type II superconductor, the magnetic field starts to penetrate the sample at 3Cc, 1, a magnetic field less than rXc, the thermodynamic critical field. Superconductivity remains in the so-called vortex state between 9 c and Ci2 until WCt2 is attained. At this magnetic field, complete penetration occurs, and the sample becomes a normal conductor.

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