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Coexistence between long-range magnetic order and spin fluctuations in intermetallic EuCu2(Si,Ge)2


Rare-earth intermetallic compounds provide unique opportunities for furthering our understanding of magnetism in solids. In mixed-valence or heavy-fermion systems, the hybridization between local f orbitals and conduction band states can cause the suppression of long-range magnetic order, which competes with strong spin fluctuations. Using different microscopic probes (XANES, Mössbauer spectroscopy, elastic and inelastic neutron scattering) we have studied in detail the EuCu2(SixGe1−x)2 series, where Eu valence can be tuned by varying the Si/Ge ratio. Our results support the persistence of valence fluctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration xc ≈ 0.65. The sequence of magnetic ground states in the series is shown to reflect the evolution of the magnetic spectral response.

K.S. Nemkovski et al., Phys. Rev. B 94, 195101 (2016).