Al-Ge-Mn and Al-Cu-Ge-Mn quasi-crystals with coercivity at room temperature

Icosahedral quasi-crystals with coercivity at room temperature are found in rapidly solidified Al-Ge-Mn and Al-Cu-Ge-Mn alloys with compositions ranging form 20 to 25 at%Ge, 22.5 to25%Mn and 0 to 10%Cu. The highest Curie temperature is 533 K for Al_52.5Ge_22.5Mu₂₅and 467 K for Al₄₀Cu₁₀Ge₂₅Mn₂₅The magnetization (σ₂₀) of the Al-Ge-Mn alloys in a field of 20 kOe at roomtemperature increases from 0.2 to 0.5 emu/g with increasing Ge and Mn contents and the coercivity(H_c) is in the range of 0.7 to 1.1 kOe. The replacement of Al by 10%Cu is found to bring about significant increases of σ₂₀and H_cto 3.9 emu/g and 1.8 kOe.