ESR experiments in the Kondo insulator CeNiSn

TL;DR

This study uses ESR to investigate the electronic gap in CeNiSn and how doping with Co or Pt affects the metal-insulator transition, providing insights into the density of states and gap evolution.

Contribution

It demonstrates the use of Gd ESR to directly measure the density of states and track the gap closing in doped CeNiSn, advancing understanding of Kondo insulator behavior.

Findings

Gd ESR linewidth correlates with the density of states at the Fermi level.

The size of the electronic gap can be estimated from ESR data.

Doping with Co or Pt closes the gap, as observed through ESR, NMR, and thermodynamic measurements.

Abstract

Below a characteristic temperature, due to hybridisation effects Kondo insulators exhibit a gap in the electronic density of states and behave like semiconductors. By using Gd3+ electron spin resonance (ESR), the compound CeNiSn was investigated as a representative of this class. In addition, the metal-to-insulator transition was studied as a function of doping for CeNi(1-x)Co(x)Sn and CeNi(1-y)Pt(y)Sn. The linewidth of the Gd resonance yields direct information about the density of states at the Fermi energy. So the size of the gap can clearly be estimated for the pure compound, and the closing of the gap by substitution of Ni by Co or Pt can be followed in detail. These results are compared to measurements of NMR, specific heat and susceptibility.