31P-NMR and muSR Studies of Filled Skutterudite Compound SmFe4P12: Evidence for Heavy Fermion Behavior with Ferromagnetic Ground State

TL;DR

This study uses 31P-NMR and muSR techniques to investigate SmFe4P12, revealing heavy fermion behavior, Kondo effects, and ferromagnetic order at low temperatures, contributing to understanding of correlated electron systems in filled skutterudites.

Contribution

It provides new experimental evidence of heavy fermion behavior and ferromagnetic ground state in SmFe4P12 through combined NMR and muSR measurements.

Findings

Kondo-like temperature dependence of relaxation rate 1/T1

Ferromagnetic order below 1.6 K

Crystalline electric field splitting of Sm3+ multiplet

Abstract

The 31P-NMR (nuclear magnetic resonance) and muSR (muon spin relaxation) measurements on the filled skutterudite system SmFe4P12 have been carried out. The temperature T dependence of the 31P-NMR spectra indicates the existence of the crystalline electric field effect splitting of the Sm3+$ (J = 5/2) multiplet into a ground state and an excited state of about 70 K. The spin-lattice relaxation rate 1/T1 shows the typical behavior of the Kondo system, i.e., 1/T1 is nearly T independent above 30 K, and varies in proportion to T (the Korringa behavior, 1/T1 \propto T) between 7.5 K and 30 K. The T dependence deviated from the Korringa behavior below 7 K, which is independent of T in the applied magnetic field of 1 kOe, and suppressed strongly in higher fields. The behavior is explained as 1/T1is determined by ferromagnetic fluctuations of the uncovered Sm3+ magnetic moments by conduction electrons. The muSR measurements in zero field show the appearance of a static internal field associated with the ferromagnetic order below 1.6 K.