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. ${\mathrm{Cu}}_{0.99}$ ${\mathrm{Fe}}_{0.01}$ films sputtered at 800 °C show a large amount of clustering, while films deposited at room temperature do not. The susceptibility of the ${\mathrm{Cu}}_{0.99}$ ${\mathrm{Fe}}_{0.01}$ films deposited at room temperature follows a Curie-Weiss law from which one can extract a Kondo temperature ($T_K$) very close to 0 °K. One can deduce from the slope of ${\chi }^{-1\mathrm{}}$ versus $T$ and from the fact that $T_K\sim 0°$K that most, if not all, of the Fe atoms in such a film are paired.