Abstract

Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.

Highlights

  • Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers

  • In the Heisenberg model of localised magnetism in magnetic insulators the electrons, involved in the exchange coupling, are localised by strong electronic correlations when the large on-site Coulomb repulsion U opens a well-defined gap for charge carriers[2,3,4]; and an adequate description of the ground state properties of these systems in terms of the superexchange spin-orbital models has been suggested[5,6,7,8,9,10,11,12,13]

  • We attribute these anomalies to electronic instabilities caused by the nature of magnetism inherent in this Kondo-lattice metal, which exhibits quasi-one-dimensional characteristics at higher temperatures and spin-glass-like behaviour at lower temperatures[15,16,17,18]

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Summary

Introduction

Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3 In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors. The nature of the magnetism appears to be very complex, with strong evidence of ferromagnetic correlations and a complex ferrimagnetic type order in the basal plane, and a kind of anti- and ferromagnetic correlations perpendicular to the basal plane, along the c axis[15]

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