Magnetic Properties of Rare-Earth Monopnictides in High Magnetic Fields

Abstract

Since more than two decades, the physics of rare-earth compounds has been of particular interest because of the variety of their magnetic properties, classified as valence fluctuations and heavy fermions. In Ce compounds, the valence changes between +3 (4f1) and +2 (4f0) in some materials called valence fluctuation systems, although the valence is normally supposed to be +3 (4f1). The very small valence excitation energy for Ce and Yb leads to an intermediate valence state by hybridization between the 4f states and neigh-boring atoms, and creates a resonance scattering band near the Fermi level E F. The energy width of the band is about Δ = πN F V 2, where V is the hybridization amplitude and N F is the density of states (DOS) of the conduction band near E F. Therefore, the DOS at the Fermi surface is enhanced on the order of 1/Δ. Some of the Ce and Yb compounds show heavy-fermion behavior. A typical material is CeAl3. As a result of the enhanced DOS at E F, the effective mass is a hundred or a thousand times larger than that of the normal metals. At low temperatures, the mixing between the 4f orbital and the itinerant bands results in an excessively narrow quasi-particle band at the Fermi level. The Sommerfeld coefficient g is proportional to the DOS at E F and γ = 1.6 JK−2 mol−1 in CeAl3 [11]. While in the typical normal metal, copper, γ is about 0.7 mJK−2 mol−1. Therefore, very strong mass enhancement occurs in CeAl3. We can know only the amplitude of the total interactions between electrons from the specific heat measurements.KeywordsFermi SurfacePickup CoilMagnetic Phase DiagramFast Fourier Transform AnalysisHole PocketThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.