Magnetic properties of the quaternary Heusler alloy CoFeTiSn

Structural and magnetic properties of the quaternary Heusler alloy CoFeTiSn were investigated. The crystal structure was found to be a cubic LiMgPdSn-type with a lattice parameter a = 0.605 77(9) nm at 300 K. The magnetization curve of CoFeTiSn exhibited the ferromagnetic behavior with a spontaneous magnetization Ms = 1.06 μB/f.u. and a Curie temperature TC = 173.6 K. The obtained Ms value is close to the value predicted by the Slater-Pauling rule and first-principles band calculations for half-metallic ferromagnets. The determination of spectral parameters T0 and TA based on Takahashi’s spin fluctuation theory suggests that spin fluctuations were suppressed relative to those in typical itinerant ferromagnets. The square of the spontaneous magnetic moment ps2(T) was proportional to T4/3 in wide temperature range up to TC. The experimental results reveal that the spin fluctuation theory for weak itinerant electron ferromagnets is applicable even to CoFeTiSn with moderately localized Co and Fe atoms.