Abstract
Three-dimensional geometrically frustrated itinerant magnet is investigated based on the single band Hubbard model on the pyrochlore lattice. The magnetic correlation and the quasiparticle properties are discussed by the weak correlation approach for half-filled case, based on the single electron spectrum in consideration of the lattice geometry. The spectrum reveals the existence of doubly degenerate flat band over the whole Brillouin zone. The spin fluctuation spectrum in RPA is anisotropic and shows the independence on frequency. The result is globally consistent with the observed in Y(Sc)Mn2. It is also shown that the frequency spectrum is clearly different from the conventional Fermi liquid one, which brings the breakdown of the Fermi liquid picture owing to the divergence of quasiparticle mass.
