Magnetic, electronic and Shubnikov-de Haas investigation of the dense Kondo system CeAgSb2

TL;DR

This study investigates the magnetic, electronic, and quantum oscillation properties of the dense Kondo system CeAgSb2, revealing complex magnetic phases, non-Fermi liquid behavior, and small Fermi surface features through comprehensive experimental techniques.

Contribution

It provides a detailed experimental analysis of CeAgSb2's magnetic phases, Fermi surface topology, and scattering mechanisms, highlighting novel insights into its complex magnetic ground state.

Findings

CeAgSb2 exhibits both ferro- and antiferromagnetic order below 9.8 K.

Resistivity behavior suggests additional scattering from bosonic excitations with an energy gap.

Fermi surface measurements reveal small sections and sensitivity to magnetic field orientation.

Abstract

Of the dense Kondo materials in the class CeTSb2 (where T = Au, Ag, Ni, Cu, or Pd), CeAgSb2 is special due to its complex magnetic ground state, which exhibits both ferro- and anti-ferromagnetic character below an ordering temperature TO ~ 9.8 K. To further elucidate a description this magnetic ground state, we have carried out a systematic study of single crystalline CeAgSb2 by magnetic, electrical magneto-transport, and Shubnikov-de Haas (SdH) studies over a broad range of temperature and magnetic field. We have constructed the magnetic phase diagram based solely on magnetoresistance data. Here, depending on the orientation of the magnetic field H, either ferromagnetic or antiferromagnetic ordering occurs below TO. The resistivity of this compound below TO does not follow a simple Fermi liquid behavior, but requires an additional contribution from conduction electron scattering from boson excitations with an energy gap, D. At zero field the temperature dependent resistivity below TO is most consistent with antiferromagnetic order, based on the transport theory which includes magnon scattering. Crystal field effect theory applied to the susceptibility data yields splitting energies from the ground state to the first and second excited states of 53 K and 137 K, respectively. Although there is some uncertainty in the Kondo temperature determination, we estimate TK ~ 23 K from our analysis. In the Fermi surface studies, the measurements show very small Fermi surface sections, not predicted by band structure calculations, and the SdH amplitudes are very sensitive to field direction. Only by considering lens orbits between the main Fermi surface cylinders can the SdH results be reconciled with the Fermi surface topology predicted from band structure.