Hyperfine Fields of Non-Magnetic Atoms in Ferromagnetic Heusler Alloys: Co₂TiAl and Co₂TiGa

Abstract

The hyperfine fields of Ti^47,49, Al²⁷ and Ga^69,71 in ferromagnetic Heusler alloys Co₂TiAl and Co₂TiGa are measured, and the Knight shifts of Al²⁷ and Ga^69,71 are also measured in the paramagnetic state above the Curie temperature. The hyperfine fields of Ti^47,49 are −24.1±0.4 kOe in Co₂TiAl and −26.6±0.4 kOe in Co₂TiGa. They contrast with the positive fields of Co⁵⁹. The hyperfine field of Al²⁷ in Co₂TiAl is −1.78±0.2 kOe and that of Ga^69,71 in Co₂TiGa is +2.76±0.2 kOe. The Knight shifts at high temperature limit are +0.06% for Al²⁷ and +0.16% for Ga^69,71. These small fields and Knight shifts originate from the reduction of the density of s electrons at Fermi level as seen for Al in alloys with transition elements.