Low temperature calorimetric and magnetic properties of Al-Mn and Al-Mn-Si quasi-crystals

The authors report the low temperature specific heat Cp and magnetic measurements for solid solution Al-3at.percent Mn, Al86Mn14 and Al25Mn20Si5 in quasi-crystalline phases. From the amplitude of the electronic specific heat determined below 0.3K, they propose that the large density of states in the crystalline phases are due to virtual bound states related to a regime of isolated manganese impurities. Both Cp and magnetic measurements indicate a rapid evolution of the magnetic interactions from Al86Mn14 to Al25Mn20Si5. In the latter, the Χac data together with the nuclear magnetic hyperfine specific heat confirm a spin glass state similar to that of canonical spin glasses such as Cu-Mn and Au-Mn. A small fraction of Mn s atoms are magnetic sites (probably less than 10 percent) in both quasi-crystalline phases.