Magnetic Properties of Cu-Mn and Cu-Fe Alloys

Cu-Mn alloys with a Mn content ranging from 5 to 30 at.% were sputtered at temperatures ranging from 77 to 1070^∘{}K. The films deposited at 77 ^∘{}K showed an antiferromagnetic spin ordering. On the other hand, films deposited at 1070 ^∘{}K had the mixed antiferromagnetic-ferromagnetic behavior of the bulk which can be explained by an exchange-anisotropy mechanism. Films deposited at 170 or 300 ^∘{}K displayed a ferromagnetism similar to that observed with superparamagnetic particles with a Curie temperature proportional to the Mn content. These magnetic properties are consistent with the idea that the low-temperature-deposited films (77 ^∘{}K) have a random distribution of Mn atoms and that the degree of clustering of Mn atoms increases with increasing deposition temperature. Cu0.99{Fe}0.01films sputtered at 800 ^∘C show a large amount of clustering, while films deposited at room temperature do not. The susceptibility of the{Cu}0.99Fe0.01 films deposited at room temperature follows a Curie-Weiss law from which one can extract a Kondo temperature (TK) very close to 0 ^∘{}K. One can deduce from the slope of χ^-1 versus T and from the fact that TK~0^∘K that most, if not all, of the Fe atoms in such a film are paired.