Itinerant Ferromagnetism for Mixed Valence Systems

Abstract

We introduce a novel mechanism for the unusual itinerant ferromagnetism found in mixed valence systems like Ce(Rh${}_{1-x}$Ru${}_x$)${}_3$B${}_2$, La${}_x$Ce${}_{1-x}$Rh${}_3$B${}_2$, US, USe, and UTe. With it we can provide an explanation for the long-unexplained large value of $T_c$ ($\sim$ 100${}^{\circ }$K) value and the maximum in the magnetization below $T_c$ found experimentally. We also show that this novel itinerent ferromagnetism can be continuously connected with the localized case for which the energy scale is much smaller ($J_{RKKY}\sim$ 1${}^{\circ }$K).

5 pages 3 figures