Excitations and magnetization density distribution in a dilute ferromagnetic semiconductor

Abstract

Yb$_{14}$MnSb$_{11}$ is a rare example of a Kondo lattice compound with ferromagnetic dominated RKKY interactions. As a ferromagnetic semiconductor with $T_c approx 53$~K, it is also a potential compound for exploration of spintronic devices. This material is furthermore one of the most efficient high temperature thermoelectrics. Here we describe measurements which answer remaining questions regarding the energy scales of the exchange interactions, the valence and the magnetization density distribution in this system. We find that the system consists of RKKY exchange coupled Mn$^{2+}$ sites with nearest and next nearest exchange interactions dominating the magnetic spectrum with no significant magnetization density localized on other atomic sites. The extended spread of a negative magnetization around each of the Mn ions supports a Kondo screening cloud scenario for Yb$_{14}$MnSb$_{11}$.