Anomalous low temperature state of CeOs4Sb12: Magnetic field and La-impurity study

TL;DR

This study investigates the low-temperature behavior of CeOs4Sb12, revealing an intrinsic transition associated with a Fermi surface gap that is highly sensitive to La impurities and magnetic fields.

Contribution

It provides new insights into the intrinsic nature of the 1.1 K transition and its suppression by La impurities, along with magnetic field effects on specific heat.

Findings

The 1.1 K transition is intrinsic and involves a Fermi surface gap.

La impurities suppress the transition and decrease the electronic specific heat.

Magnetic fields produce anomalous responses in the specific heat.

Abstract

Specific heat for single crystalline samples of Ce1-xLaxOs4Sb12 at zero-field and magnetic fields to 14 T is reported. Our results confirm enhanced value of the electronic specific heat coefficient in the paramagnetic state. They provide arguments for the intrinsic origin of the 1.1 K anomaly. This transition leads to opening of the gap at the Fermi surface. This low temperature state of CeOs4Sb12 is extremely sensitive to chemical impurities. 2% of La substituted for Ce suppresses the transition and reduces the electronic specific heat coefficient. The magnetic field response of the specific heat is also anomalous.