The radial dependence of the magnetic hyperfine field for Sn atoms in the ferromagnetic Heusler alloys

The magnetic hyperfine fields, Bsub(h)sub(f), for impurity 119Sn atoms in Z sites of ferromagnetic Heusler alloys Co2 MnZ(Z = Si,Ge) are measured by the Moessbauer effect. At 77 K Bsub(h)sub(f) = -1.43 +- 0.04 +- 0.05 T in Co2 MnSi and Bsub(h)sub(f) = + 1.05 T in Co2 MnGe. From the comparison between the values of Bsub(h)sub(f) for Sn atoms in Co2 MnZ(Z = Si,Ge,Sn), it follows that the negative contribution to Bsub(h)sub(f) drops as the interatomic distance begins to increase. This radial dependence also manifests itself in the anomalies of the temperature dependences of the hyperfine fields. The temperature anomaly is positive vor Sn in Co2MnGe and negative for Sn in Co2MnSi. (orig.)