L. M. Holanda | Searcharxiv

arXiv2011

Eu2+ spin dynamics in the filled skutterudites EuM4Sb12 (M = Fe, Ru, Os)

We report evidence for a close relation between the thermal activation of the rattling motion of the filler guest atoms, and inhomogeneous spin dynamics of the Eu2+ spins. The spin dynamics is probed directly by means of Eu2+ electron spin resonance (ESR), performed in both X-band (9.4 GHz) and Q-band (34 GHz) frequencies in the temperature interval 4.2 < T < 300 K. A comparative study with ESR measurements on the Beta-Eu8Ga16Ge30 clathrate compound is presented. Our results point to a correlation between the rattling motion and the spin dynamics which may be relevant for the general understanding of the dynamics of cage systems.

cond-mat.str-el↗

arXiv2009

Evidence for the existence of Kondo coupled resonant modes in heavy fermions

Electron Spin Resonance (ESR) can microscopically probe both conduction electrons (ce) and local moment (LM) spin systems in different materials. A ce spin resonance (CESR) is observed in metallic systems based on light elements or with enhanced Pauli susceptibility. LM ESR is frequently seen in compounds with paramagnetic ions and localized d or f electrons. Here we report a remarkable and unprecedented ESR signal in the heavy fermion (HF) superconductor beta-YbAlB4[1] which behaves as a CESR at high temperatures and acquires characteristics of the Yb3+ LM ESR at low temperature. This dual behavior in same ESR spectra strikes as an in situ unique observation of the Kondo quasiparticles giving rise to a new ESR response called Kondo coupled resonant mode (KCRM). The proximity to a quantum critical point (QCP) may favor the observation of a KCRM and its dual character in beta-YbAlB4 may unveil the 4f-electrons nature at the QCP.

cond-mat.str-el↗