Magnetic spin resonance inCeB6

Abstract

Line shape of magnetic spin resonance at 60 GHz specific to the phase II (so-called antiferroquadrupole phase) of ${\text{CeB}}_{6}$ was studied. The applied procedure of data analysis has allowed obtaining $g$ factor of the oscillating magnetic moments, line width, and oscillating magnetization. It is found that the approaching to the transition temperature ${T}_{\text{I-II}}$ from phase II to the paramagnetic phase I results in strong broadening of the resonance (the line width increases three times in the range $1.8\text{ }\text{K}\ensuremath{\le}T\ensuremath{\le}3.8\text{ }\text{K}$) whereas $g$ factor $g=1.59$ remains temperature independent. Magnetic-resonance data suggests that the magnetization of ${\text{CeB}}_{6}$ in the phase II consists of several contributions, one of which is responsible for the observed magnetic resonance. This term in magnetization is missing in the paramagnetic phase and corresponds to ferromagnetically interacting localized magnetic moments. The magnitude of the oscillating part of magnetization is less than total magnetization in the range ${T}^{\ensuremath{\ast}}\ensuremath{\le}T\ensuremath{\le}{T}_{\text{I-II}}$ and coincides with the total magnetization for $T\ensuremath{\le}{T}^{\ensuremath{\ast}}$, where ${T}^{\ensuremath{\ast}}\ensuremath{\sim}2\text{ }\text{K}$. We argue that ferromagnetic correlations play a key role in the observed phenomenon in analogy with the recent experimental and theoretical results on the magnetic resonance in the dense Kondo systems. At the same time the interpretation of the magnetic-resonance data in the framework of the existing models of magnetism in ${\text{CeB}}_{6}$ faces substantial difficulties, which demands further development of the theory of static and dynamic magnetic properties of this heavy fermion metal.