Effects of Eu doping on SmB6single crystals

Sunmog Yeo,Kimyung Song,Pedro Schlottmann,Namjung Hur,Z Fisk

doi:10.1103/physrevb.85.115125

Abstract

The various phases in Sm${}_{1\ensuremath{-}x}$Eu${}_{x}$B${}_{6}$ are investigated based on magnetic susceptibility, resistivity, and Hall effect measurements. The end compounds are a Kondo insulator (SmB${}_{6}$) and a polaronic ferromagnet (EuB${}_{6}$). For $x$ \ensuremath{\approx} 0.2, the ground state undergoes a transition from a Kondo insulator to an antiferromagnetic (AF) insulator phase. Further doping induces a transition to an AF metal at $x$ \ensuremath{\approx} 0.4. The spin gap is reduced rapidly with the Eu substitution, while there is a charge gap up to $x$ \ensuremath{\approx} 0.4. The Hall effect indicates a dramatic decrease in the carrier density at low temperatures ($T$) for the Kondo insulator regime, whereas, the carrier density is almost independent of $T$ in the AF metallic phase.

Highlights

The intriguing physical properties of the Kondo insulatorSmB6 and the magnetic-polaron-induced ferromagnetic (FM)phase of EuB6 have been the topics of numerous papers
The various phases in Sm1−xEuxB6 are investigated based on magnetic susceptibility
the ground state undergoes a transition from a Kondo insulator to an antiferromagnetic (AF

Summary

INTRODUCTION

Phase of EuB6 have been the topics of numerous papers. The compound Sm1−xEuxB6 forms for all values of x and is expected to have a rich phase diagram due to the sensitivity of SmB6 to pressure and the interplay of FM and antiferromagnetic (AF) correlations. We show that, with increasing x, the ground state of Sm1−xEuxB6 undergoes a sequence of phase transitions from Kondo insulator to AF insulator to AF metal and to the polaron-driven FM state. As a function of pressure, SmB6 undergoes a first-order phase transition to a magnetically ordered metallic state with features of the 4f 55d configuration at a critical pressure pc ≈ 6 GPa.. Kondo insulators are close to an AF phase transition, these La and Yb substitutions do not give rise to an AF phase nor does a small amount of magnetic doping, such as Eu and Gd.. In view of the competition of FM and AF correlations and the nonmagnetic insulator and FM metallic ground states of the end-point compounds SmB6 and EuB6, the Sm1−xEuxB6 system is expected to probe, as a function of x, various magnetic phases and an insulator-to-metal transition As a function of pressure, SmB6 undergoes a first-order phase transition to a magnetically ordered metallic state with features of the 4f 55d configuration at a critical pressure pc ≈ 6 GPa. A La3+ substitution for Sm causes a decrease in the Sm valence, whereas, a Yb2+ substitution increases the Sm valence. Kondo insulators are close to an AF phase transition, these La and Yb substitutions do not give rise to an AF phase nor does a small amount of magnetic doping, such as Eu and Gd. 5% Sm doping in EuB6 has been reported to suppress the FM metallic phase and to cause an AF metallic phase. in view of the competition of FM and AF correlations and the nonmagnetic insulator and FM metallic ground states of the end-point compounds SmB6 and EuB6, the Sm1−xEuxB6 system is expected to probe, as a function of x, various magnetic phases and an insulator-to-metal transition

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