Ferromagnetic fluctuations in YbNi4P2 measured by inelastic neutron scattering

Z Huesges,T Fennell,J P Embs,C Geibel,C Krellner,M M Koza,G Simeoni,O Stockert

doi:10.1088/1742-6596/592/1/012083

Abstract

YbNi4P2 is one of the very few heavy-fermion systems which allow the study of ferromagnetic quantum criticality. The Curie temperature TC=0.17 K can be suppressed by substituting arsenic on the phosphorus site, without changing the ferromagnetic nature of the ordered state. The ordered moment, even of the unsubstituted compound, is only around 0.05 μB, which hinders elastic neutron scattering experiments. To gain microscopic insight into the nature of the interactions, we have studied the magnetic excitations of polycrystalline YbNi4P2 by time-of-flight neutron spectroscopy. For momentum transfers larger than about 0.6 Å−1 we find a quasi-elastic response whose width at low temperatures is limited by the Kondo effect. In contrast, the low-energy magnetic response is distinctly different for Q approaching zero: At low temperatures, but still in the paramagnetic phase, susceptibility and lifetime of the spin fluctuations are strongly enhanced, indicating the proximity of ferromagnetism.

Highlights

YbNi4P2 is one of the very few heavy-fermion systems which allow the study of ferromagnetic quantum criticality
For momentum transfers larger than about 0.6 ̊A−1 we find a quasi-elastic response whose width at low temperatures is limited by the Kondo effect
Quantum critical points (QCPs) in intermetallic systems continue to be a topic of strong interest in condensed matter physics, due to the appearance of non-Fermi-liquid behaviour and exotic phases in their proximity [1]

Summary

Introduction

Quantum critical points (QCPs) in intermetallic systems continue to be a topic of strong interest in condensed matter physics, due to the appearance of non-Fermi-liquid behaviour and exotic phases in their proximity [1]. For momentum transfers larger than about 0.6 ̊A−1 we find a quasi-elastic response whose width at low temperatures is limited by the Kondo effect. The low-energy magnetic response is distinctly different for Q approaching zero: At low temperatures, but still in the paramagnetic phase, susceptibility and lifetime of the spin fluctuations are strongly enhanced, indicating the proximity of ferromagnetism.

Results

Conclusion