A new unconventional antiferromagnet,

Abstract

We report the synthesis and basic properties of single crystals of a new binary compound, Yb3Pt4. The Yb ions in this compound are fully trivalent, and heat capacity measurements show that the crystal field scheme involves a doublet ground state, well separated from the excited states, which are fully occupied above ∼ 150 K. The heat capacity displays a large, weakly first order anomaly at 2.4 K, where a cusp is observed in the magnetic susceptibility signalling the onset of antiferromagnetic order. The entropy associated with this order is the full Rln2 of the doublet ground state, however the magnetic susceptibility in the ordered phase is dominated by a large and temperature independent component below the Neel temperature. The heat capacity in the ordered state originates with ferromagnetic spin waves, giving evidence for the inherently local moment character of the ordered state. The electrical resistivity is unusually large, and becomes quadratic in temperature exactly at the Neel temperature. The absence of analogous Fermi liquid behavior in the heat capacity and the magnetic susceptibility implies that Yb3Pt4 is a low electron density system, where the Fermi surface is further gapped by the onset of magnetic order.

Determination of the magnetic structure ofYb3Pt4:k=0local-moment antiferromagnet

“…3 and are summarized in Table I. In accordance with detailed work on single crystals 7 , we found that variations of the site occupancies were insignificant, and therefore we fixed the sites to be fully occupied. The refined coordinates for the Yb-18f and the Pt-18f are very similar to the room temperature values found by Palenzona and, in more detail, by Bennett et al 7,13 .…”

“…These results indicate a magnetic ordering temperature of about 2.4 K, in excellent agreement with our previous results from specific heat, dc and ac magnetic susceptibility, and electrical resistivity. 6,7 . As was also the case in these earlier measurements, we observed neither thermal hysteresis nor a sudden change in this order parameter near T N , suggesting that the ordering transition is continuous and well-described by a mean-field expression.…”

“…Different scenarios 4 can be related to antiferromagnetic (AF) QCPs either involving large localized-moment order or involving small-moment spindensity wave-like order. We have recently 6,7 identified the binary intermetallic compound Yb 3 Pt 4 as a stoichiometric Yb-based compound with a field-induced quantum critical point (QCP).…”

“…We have characterized Yb 3 Pt 4 by measuring thermodynamic and transport properties 6,7 . The magnetic susceptibility χ of Yb 3 Pt 4 above 200 K is well-described by a Curie-Weiss expression involving the full Yb 3+ moment of 4.5 µ B .…”

Localized moments and the stability of antiferromagnetic order in Yb3Pt4

“…Single crystals of Yb 3 Pt 4 were grown from lead flux 20,21 , yielding rod-like crystals with approximate dimensions of 1 × 1 × 5 mm. Powder X-ray diffraction measurements were used to verify that the crystals form in the reported rhombohedral Pu 3 Pd 4 structure type 24 .…”