Intercalation and Substitution Effects of Si in Weak Itinerant Ferromagnetic Ni3Al

The Si-intercalated compounds Ni 3 AlSi x ( x = 0, 0.01, 0.02, 0.05, 0.07, and 0.1) and Si substituted compounds Ni 3 Al 1- y Si y ( y = 0, 0.01, 0.015, 0.02, 0.04, 0.06, 0.1, and 0.2) were synthesized and investigated by macroscopic and microscopic magnetic measurements. We found that the common features to these two systems are: (i) drastic disappearance of ferromagnetism in Ni 3 Al with only a small Si concentration x c ≃0.01 or y c ≃0.02, (ii) T 4/3 -temperature dependences in both square spontaneous magnetization M (0, T ) 2 and inverse initial susceptibility χ 0 -1 near the Curie temperature T C for ferromagnetic metal. T 4/3 -temperature dependence of χ 0 -1 are found to hold even for the paramagnetic metals that are classified as nearly itinerant ferromagnets very close to the ferromagnetic instability. On the other hand, our 27 Al NMR results show that the Si intercalation leads to the changes of the hyperfine coupling constant A hf , the characteristic parameters of spin fluctuations, T 0 and T ...