Molecular-Field Theory of a Random Ising System in the Presence of an External Magnetic Field

摘要: The thermodynamic properties of very dilute concentrations magnetic impurities in a nonmagnetic system and the presence an externally applied field are examined, using mean-random-field approximation. assumed to interact via long-range potential which alternates sign as function position between ions. A modified form Margenau's statistical model is used obtain probability distribution $P(\overline{H})$ random internal exchange fields $\overline{H}$ Ising model. magnetization specific heat obtained integrals over fields. variation low-temperature external for all temperatures. model, when alloy system, shows that excess very-low-temperature strongly decreased by ${H}_{\mathrm{ext}}$. per impurity predicted be proportional ${\mathrm{tan}}^{\ensuremath{-}1}$ $\frac{{H}_{\mathrm{ext}}}{\ensuremath{\Delta}}$, where $\ensuremath{\Delta}$ temperature- external-field-dependent width distribution.