Spin Gap in Heavy Fermion UBe${}_{13}$

Abstract

Muon spin rotation (${\mu }^{+}$SR) experiments have been carried out in the heavy fermion compound UBe${}_{13}$ in the temperature range from 0.025 K to 300 K and in magnetic fields up to 7 T, supported by resistivity and magnetization measurements. The ${\mu }^{+}$SR spectra are characteristic of formation of a spin polaron which persists to the lowest temperature. A gap in the spin excitation spectrum of f-electrons opens up at about 180 K, consistent with anomalies discovered in resistivity, heat capacity, NMR and optical conductivity measurements of UBe${}_{13}$.

5 pages, 4 figures, 38 references