Magnetic Susceptibility of Dilute Al-Mn Alloys

Abstract

The temperature dependence of the magnetic susceptibility of pure aluminum and three aluminum alloys containing 0.045, 0.21, and 0.35 at.% manganese has been measured between 2 and 300 \ifmmode^\circ\else\textdegree\fi{}K. All of the susceptibility results can be fitted to an equation of the form $A+B{T}^{2}$. The experimental values of the coefficients $A$ and $B$ for pure aluminum are 19.2 \ifmmode\pm\else\textpm\fi{} 0.1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}7}$ emu/cc and 3.7 \ifmmode\pm\else\textpm\fi{} 0.1 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}12}$ emu/cc/(\ifmmode^\circ\else\textdegree\fi{}${\mathrm{K}}^{2}$), which are in good agreement with theoretical values derived from the known band structure of aluminum. An additional susceptibility component is observed in th Al-Mn alloys, and the experimental results can be characterized by the equation $\frac{\ensuremath{\Delta}{K}_{\mathrm{Mn}}(T)}{C}$ emu/cc at.% $\mathrm{Mn}=13.8\ifmmode\pm\else\textpm\fi{}0.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}\ensuremath{-}(14\ifmmode\pm\else\textpm\fi{}3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}){T}^{2}$. The experimentally determined coefficients can be explained by considering an exchange enhancement of the Pauli paramagnetism within the framework of a Hartree-Fock approximation. Values of the exchange enhancement factor $\ensuremath{\eta}$, and the width of the virtual bound $d$ states, $\ensuremath{\Delta}$, can be uniquiely determined and have the values 4.4 \ifmmode\pm\else\textpm\fi{} 1 and 0.33 \ifmmode\pm\else\textpm\fi{} 0.05 eV, respectively.