Abstract
We present magnetization, specific heat, and NMR investigations on over a wide range in temperature and magnetic field. The magnetic susceptibility at low temperatures is strongly enhanced at weak magnetic fields, accompanied by a divergence of the low- specific heat coefficient in zero field, which indicates a ground state of correlated electrons. From our hard-x-ray photoemission spectroscopy study, the Yb valence at 50 K is evaluated to be 2.38. The system displays valence fluctuating behavior in the low to intermediate temperature range, whereas above 400 K, carries a full and stable moment, and Fe carries a moment of about . The enhanced value of the Sommerfeld-Wilson ratio and the dynamic scaling of the spin-lattice relaxation rate divided by with static susceptibility suggests admixed ferromagnetic correlations. simultaneously tracks the valence fluctuations from the Yb ions in the high temperature range and field dependent antiferromagnetic correlations among partially Kondo screened Fe moments at low temperature; the latter evolve out of an Yb admixed conduction band.
- Received 19 February 2014
DOI:https://doi.org/10.1103/PhysRevLett.113.216403
© 2014 American Physical Society