High-temperature ferromagnetism in amorphous semiconductor Ge_3Mn thin films

摘要

The Ge_(1-x)Mn_x thin films were fabricated at x=0.25, of which the composition is close to Ge_3Mn. They showed ferromagnetism up to above 350 K, even though their structure is amorphous. Ge_3Mn amorphous samples grown at 200℃ have n-type characteristics, while those grown at 500℃ have p-type characteristics. The former has a different state from the latter, energetically. It is suggested that the different short range orders of Ge_3Mn_5 and/or Ge_8Mn_(11) have already formed in the amorphous phase according to the growth temperature. The authors have also discussed the relationship between ferromagnetism and cluster formations after annealing at 800℃.