Colossal Magnetoresistance and Heavy Fermions in Eu0.9Yb0.1B6 System

Current work presents the study of transport characteristics [resistivity, transverse magnetoresistance (TMR), Hall effect] of a high-quality polycrystalline sample of Eu0.9Yb0.1B6 compound in the temperature range of 2–300 K, in magnetic fields up to 8 T. The obtained data confirm the realization in Eu0.9Yb0.1B6 of a state with electronic and magnetic phase separation (EMPS), which is typical for parent europium hexaboride. For EMPS the “metallization” of the system (TM ≈ 15 K) precedes ferromagnetic (FM) ordering (TC ≈ 11.4 K). In the temperature range TC−TM, the enhancement of the colossal magnetoresistance (CMR) effect was detected. It was registered that a maximum value of –∆ρ/ρ ≈ 89% is achieved at TM point. The analysis performed allows estimating the effective mass of the electrons as mₑ* ≈ 0.9–20m0, which confirms the formation of heavy fermions in the paramagnetic (PM) phase of Eu0.9Yb0.1B6. To explain mentioned effects the polaronic scenario is proposed.