Inelastic neutron scattering study of crystalline electric field excitations in the caged compounds NdT2Zn20 (T = Co, Rh, and Ir)

TL;DR

This study investigates the crystalline electric field excitations in NdT2Zn20 compounds using inelastic neutron scattering, revealing key excitation energies and confirming ground state properties relevant for the two-channel Kondo effect.

Contribution

First detailed INS analysis of CEF excitations in NdT2Zn20 compounds, identifying excitation energies and ground state characteristics crucial for understanding Kondo physics.

Findings

Dispersionless excitations observed at specific energies for each T element.

CEF ground state confirmed as Gamma 6 doublet for all compounds.

Identification of a phonon-related shoulder near the CEF excitation in NdCo2Zn20.

Abstract

We have measured crystalline electric field (CEF) excitations of Nd3+ ions in the two-channel Kondo lattice candidates NdT2Zn20 (T = Co, Rh, and Ir) by means of inelastic neutron scattering (INS). In the INS measurements at 5 K, dispersionless excitations were observed at 3.8 and 7.2 meV for T = Co, 3.1 and 5.8 meV for T = Rh, and 3.0 and 5.3 meV for T = Ir. Analyses of the temperature dependence of the INS spectra confirm that the CEF ground states are the Gamma 6 doublet, that is a requisite for manifestation of the magnetic two-channel Kondo effect. For T = Co, a shoulder was observed at 7.7 meV close to the CEF excitation peak centered at 7.2 meV. The shoulder is attributed to a bound state of the CEF and low-lying optical phonon excitations.