Crystal fields, disorder, and antiferromagnetic short-range order in Yb0.24Sn0.76Ru

TL;DR

This study investigates the electronic and magnetic properties of Yb0.24Sn0.76Ru, revealing local moment behavior, crystal field splitting, and short-range antiferromagnetic order at low temperatures, with no long-range magnetic order observed.

Contribution

The paper provides detailed experimental characterization of a disordered Yb-based compound, highlighting its crystal field effects and evidence for short-range magnetic correlations.

Findings

Yb exhibits a stable trivalent state with no divalent component.

Crystal field splits Yb3+ into a doublet and a quartet, with specific energy levels.

Evidence suggests antiferromagnetic short-range order coexists with Kondo-like behavior.

Abstract

We report extensive measurements on a new compound (Yb0.24Sn0.76)Ru that crystallizes in the cubic CsCl structure. Valence band photoemission and L3 x-ray absorption show no divalent component in the 4f configuration of Yb. Inelastic neutron scattering (INS) indicates that the eight-fold degenerate J-multiplet of Yb3+ is split by the crystalline electric field (CEF) into a {\Gamma}7 doublet ground state and a {\Gamma}8 quartet at an excitation energy 20 meV. The magnetic susceptibility can be fit very well by this CEF scheme under the assumption that a {\Gamma}6 excited state resides at 32 meV; however, the {\Gamma}8/{\Gamma}6 transition expected at 12 meV was not observed in the INS. The resistivity follows a Bloch- Gr\"uneisen law shunted by a parallel resistor, as is typical of systems subject to phonon scattering with no apparent magnetic scattering. All of these properties can be understood as representing simple local moment behavior of the trivalent Yb ion. At 1 K, there is a peak in specific heat that is too broad to represent a magnetic phase transition, consistent with absence of magnetic reflections in neutron diffraction. On the other hand, this peak also is too narrow to represent the Kondo effect in the {\Gamma}7 ground state doublet. On the basis of the field-dependence of the specific heat, we argue that antiferromagnetic shortrange order (possibly co-existing with Kondo physics) occurs at low temperatures. The long-range magnetic order is suppressed because the Yb site occupancy is below the percolation threshold for this disordered compound.