Anomalous Low-Lying Thermal Excitations Deep Inside the Ferromagnetic State in Filled Skutterudite NdFe

概要

論文の詳細を見る
The low-temperature properties of NdFe<inf>4</inf>As<inf>12</inf>single crystals grown by the As self-flux method under high pressure have been studied by magnetization, electrical resistivity, and specific heat measurements. We found that NdFe<inf>4</inf>As<inf>12</inf>shows a ferromagnetic transition at T_{\text{c}}=14.6 K. Moreover, we found additional anomalies, a shoulder in the resistivity and a Schottky-like peak in magnetic specific heat below T_{\text{c}}. It is rare that the corresponding peak of the specific heat is larger than the specific heat jump at T_{\text{c}}. From the crystal electric field analysis of Nd 4f electrons with a simple mean field approximation, we found that a model with a quasi-degenerate sextet (doublet and quartet) reproduces these anomalous features qualitatively, but quantitative differences, probably attributable to the contribution from Fe d electrons, still remain. We also found that the effective magnetic moment (4.43 \mu_{\text{B}}/f.u.) is larger than the Nd<sup>3+</sup>free-ion value (3.67 \mu_{\text{B}}/ion), indicating the contribution of Fe itinerant magnetism.
2013-11-15