# Insight into the temperature dependent properties of the ferromagnetic Kondo lattice YbNiSn

## TL;DR

This study investigates the temperature-dependent electronic properties of YbNiSn, revealing a persistent Kondo resonance and non-Fermi liquid behavior over a broad temperature range, challenging traditional models of Kondo lattice systems.

## Contribution

It demonstrates that Kondo lattice behavior in YbNiSn extends well above T_K, with a linear increase in 4f occupancy and non-Fermi liquid characteristics, providing new insights into temperature effects in such systems.

## Key findings

- Kondo resonance persists from 100 K down to 1 K without anomalies.
- Linear increase in 4f occupancy indicates onset of Kondo screening above 100 K.
- Non-Fermi liquid behavior observed through T-linear damping in the self-energy.

## Abstract

Analyzing temperature dependent photoemission (PE) data of the ferromagnetic Kondo-lattice (KL) system YbNiSn in the light of the Periodic Anderson model (PAM) we show that the KL behavior is not limited to temperatures below a temperature T_K, defined empirically from resistivity and specificic heat measurements. As characteristic for weakly hybridized Ce and Yb systems, the PE spectra reveal a 4f-derived Fermi level peak, which reflects contributions from the Kondo resonance and its crystal electric field (CEF) satellites. In YbNiSn this peak has an unusual temperature dependence: With decreasing temperature a steady linear increase of intensity is observed which extends over a large interval ranging from 100 K down to 1 K without showing any peculiarities in the region of T_K ~ TC= 5.6 K. In the light of the single-impurity Anderson model (SIAM) this intensity variation reflects a linear increase of 4f occupancy with decreasing temperature, indicating an onset of Kondo screening at temperatures above 100 K. Within the PAM this phenomenon could be described by a non-Fermi liquid like T- linear damping of the self-energy which accounts phenomenologically for the feedback from the closely spaced CEF-states.