MOSSBAUER STUDIES OF COPPER MANGANESE ALLOYS WITH DILUTE SN-119

The Mössbauer spectra of 119Sn in face-centred cubic copper manganese alloys containing from 3 at.% to 97 at.% Mn have been obtained at 300°K, 77°K and 4·2°K, and the appearance of hyperfine fields at 119Sn nuclei as the temperature was reduced has been used to define ordering temperatures. Long range magnetic ordering has been observed in all alloys, the distributions of hyperfine fields and the ordering temperatures reflecting the change in magnetic structure at 75% Mn. The ordering is discussed. The isomer shifts for 119Sn in copper and gamma manganese with respect to white tin were determined as -0·83 ± 0·01 mm s-1 and -0.91 ± 0.02 mm s-1 respectively, and the hyperfine field at 119Sn in pure gamma manganese was found by extrapolation to be 255 ± 5 kOe.