Antiferromagnetic Correlations in Strongly Valence Fluctuating CeIrSn

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Magnetism

Background:

• Cerium (Ce) intermetallic compounds are known for complex electronic behaviors, including valence fluctuations.
• Quasikagome lattices in materials like CeIrSn can lead to unique magnetic and electronic properties due to geometrical frustration.

Purpose of the Study:

• To investigate the low-temperature physical properties of the strongly valence fluctuating compound CeIrSn.
• To understand the origin of unexpected thermal expansion and magnetostriction behaviors in CeIrSn.
• To explore the presence and nature of magnetic correlations in CeIrSn.

Main Methods:

• Hard X-ray Photoelectron Spectroscopy (HAXPES) to probe electronic states.
• Inelastic Neutron Scattering (INS) to investigate magnetic excitations.
• Thermal expansion and magnetostriction measurements to detect strain anomalies.
• Muon Spin Relaxation (μSR) to probe microscopic magnetic fields.

Main Results:

• CeIrSn displays a high Kondo temperature (T_{K}∼480 K) and strong valence fluctuations.
• Negative in-plane thermal expansion (α/T < 0) observed below 2 K, with a minimum near 0.75 K.
• Markedly negative volume and a-axis magnetostriction at low fields, transitioning before a 6 T metamagnetic anomaly.
• Muon spin relaxation measurements reveal a broad distribution of internal magnetic fields down to 0.1 K.

Conclusions:

• The observed negative thermal expansion and magnetostriction are anomalous for Ce-based intermediate valence systems.
• These behaviors suggest the emergence of antiferromagnetic correlations at very low temperatures (T ≪ T_{K}).
• Geometrical frustration in the quasikagome Ce lattice is proposed as the origin of these antiferromagnetic correlations, supported by comparison with CeRhSn.