Why rare-earth ferromagnets are so rare: insights from the p-wave Kondo model

Abstract

Magnetic exchange in Kondo lattice systems is of the Ruderman-Kittel-Kasuya-Yosida type, whose sign depends on the Fermi wave vector, $k_F$ . In the simplest setting, for small $k_F$ , the interaction is predominately ferromagnetic, whereas it turns more antiferromagnetic with growing $k_F$. It is remarkable that even though $k_F$ varies vastly among the rare-earth systems, an overwhelming majority of lanthanide magnets are in fact antiferromagnets. To address this puzzle, we investigate the effects of a p-wave form factor for the Kondo coupling pertinent to nearly all rare-earth intermetallics. We show that this leads to interference effects which for small kF are destructive, greatly reducing the size of the RKKY interaction in the cases where ferromagnetism would otherwise be strongest. By contrast, for large $k_F$, constructive interference can enhance antiferromagnetic exchange. Based on this, we propose a new route for designing ferromagnetic rare-earth magnets.

9 pages, 4 figures

References in corpus (5)

• Half-metallic ferromagnets: From band structure to many-body effects
• Superconductivity on the border of weak itinerant ferromagnetism in UCoGe
• Metallic Quantum Ferromagnets
• Kondo Breakdown in Topological Kondo Insulators
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Cited by in corpus (5)

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• Kondo-lattice ferromagnets and their peculiar order along the magnetically hard axis
• Ferromagnetic ordering along the hard axis in the Kondo lattice YbIr3Ge7
• Magnetic field-induced softening of spin waves and hard-axis order in Kondo-lattice ferromagnet CeAgSb${}_2$