Ferromagnetic Spin Fluctuation in the Itinerant-Electron Magnetic Compounds RCo₉Si₄ (R = Y, La)

Abstract

Ferromagnetic spin fluctuations in itinerant-electron magnetic compounds RCo₉Si₄ (R = Y, La) were investigated by using magnetization and ⁵⁹Co-NMR measurements. YCo₉Si₄ is an itinerant ferromagnet, while LaCo₉Si₄ is a nearly ferromagnetic metal. In YCo₉Si₄, the field dependence of the magnetization is well described by Takahashi’s spin-fluctuation theory for weak itinerant ferromagnets. In both YCo₉Si₄ and LaCo₉Si₄, the magnetic susceptibility, the Knight Shift and 1/T₁T show a similar temperature dependence, which suggests that the ferromagnetic spin fluctuation is dominant in these compounds. The difference in the magnetic ground state of these compounds is possibly attributed to the fact that the energy scale of the ferromagnetic spin fluctuation in LaCo₉Si₄ is larger than that in YCo₉Si₄.