NMR spin‐echo studies in sputtered Heusler alloy films

We have carried out at 4‐K spin‐echo studies (of 55Mn, 63Cu) on sputtered Heusler alloy (Cu2MnAl) films with substrate temperature Ts in the range of 50–300 °C in order to obtain microscopic information on the magnetic structure. For Ts =60 °C a very broad spectrum is obtained, revealing incomplete (disordered) formation of Cu2MnAl. For Ts =158, 167, 170, and 210 °C, well‐defined spectra are observed with Mn at 227 MHz and Cu at 241 and 259 MHz, respectively. Signal intensity studies reveal a maximum for Ts =167 °C in general agreement with the magnetization results of Morisako, Matsumoto, and Naoe. The signal frequencies are also in agreement with those obtained for the bulk alloy. For Ts =300 °C, the spectrum is broadened but the signal frequencies of Mn and Cu remain practically the same. This spectrum is also quantitatively different from that observed for the film with Ts=60 °C, where a low‐frequency tail is observed. The effect of post‐annealing the films is also presented.