Evidence of frustrated magnetism in CeAl3 from muon-spin-rotation spectroscopy.

Abstract

Zero-, transverse-, and longitudinal-field muon-spin-rotation (${\ensuremath{\mu}}^{+}$SR) spectroscopy was performed on polycrystalline ${\mathrm{CeAl}}_{3}$. The onset of frustrated quasistatic magnetic correlations below about 2 K, becoming partly coherent below 0.7 K, was detected. The occurrence of different components in the ${\ensuremath{\mu}}^{+}$SR signal with relative strengths showing a pronounced temperature dependence leads to the conclusion that these correlations develop in a spatially inhomogeneous, frustrated way. No evidence for a macroscopic phase transition was obtained by specific heat measurements and neutron-diffraction experiments on our sample. This indicates that the coherence length of the correlations must be very short even below 0.7 K. The effective magnetic moment was estimated to be about 0.5${\ensuremath{\mu}}_{B}$ per cerium atom. It is speculated that the observed gradual evolution of magnetism in ${\mathrm{CeAl}}_{3}$ is driven by the temperature dependence of competing magnetic interactions rather than by a divergence in the single-ion susceptibility, similar to what was recently proposed for the heavy-electron compound ${\mathrm{U}}_{2}$${\mathrm{Zn}}_{17}$.