Paramagnetic state NMR and susceptibility measurements in cobalt based Heusler alloys

Abstract

Susceptibility of Co₂TAl (T=Ti, Zr and Hf) and ⁵⁹Co and ²⁷Al Knight shifts have been measured down to the magnetic ordering temperature of these itinerant ferromagnets. The effective hyperfine fields per Bohr magneton at Co and Al nuclear sites have been derived and for Co these are in very good agreement with the spin echo results in ferromagnetic state of these alloys. The effective fields at Al site are small which is the reason that no spin echo signal due to Al could be observed. The sign of the field at Al site is accounted for in terms of an RKKY model of conduction electron polarization with appropriate preasymptotic correction.