DC Magnetization Study on Heavy-Electron Superconductor UBe₁₃

Abstract

Static DC magnetization measurements were performed in order to investigate magnetic response of the unconventional superconducting state of UBe 13. The measurements were performed on a single crystalline sample, and a magnetic field was applied for H || 001 , and H || 110. In the superconducting mixed state, an unusual magnetic anomaly was observed at a magnetic field, H * Mag , for H || 001 as well as for H || 110. This anomaly was observed both in increasing-and decreasing-field sweeps, and also in an estimated thermal-equilibrium magnetization curve. In contrast, there is no such an anomaly in the difference between the increasing-and decreasing-field magnetization curves. These facts indicate that the magnetic anomaly at H * Mag in UBe 13 is a thermodynamic anomaly, and may reflect a peculiarity of its superconducting diamagnetism or an unusual magnetic character of the electronic state in the vortex cores.

Field-Orientation Dependence of Low-Energy Quasiparticle Excitations in the Heavy-Electron SuperconductorUBe13

“…For T = 0.08 K, 8{C/T) shows a distinct positive peak around 3.5 T due to the B* anomaly. At 0.40 K, 8(C/T) changes the sign and shows a mono tonic decrease with increasing field above 2 T, reflecting the anisotropy of Hcl [43,44]. In the normal state at 0.95 K, 8{C/T) turns positive again and increases monotonically with increasing field above ~2 T. It is also remarkable that the normal-state C/T is substantially suppressed in a field of 5 T for both directions.…”

“…Accordingly, a substantial anisotropy develops in C(H) above this field. An anisotropy has also been observed by dc magnetization curves above B * [31,32]. In order to display the evolution of the anisotropy in C(H)/T , we plot in Fig.…”