LOW-TEMPERATURE NMR-STUDIES OF CE-AL COMPOUNDS

Ce-Al compounds display a variety of unconventional magnetic propertie s at low temperatures. This is particularly well demonstrated by the r esults of our low-frequency NMR studies on CeAl2, CeAl3 and Ce3Al11. A lthough CeAl2 orders antiferromagnetically below 3.4 K, the temperatur e dependence of the spin-lattice relaxation rate follows a Korringa la w below 1 K. For CeAl3, we observe an increase of the line width below 0.9 K, but no indication of a phase transition is discernible from th e temperature dependence of the spin-lattice relaxation rate. Ce3Al11 is ferromagnetic below 6.2 K, but develops an antiferromagnetic and mo dulated structure below 3.3 K. A field of the order of 3 kG, however, appears to stabilize the ferromagnetic phase. Our spectroscopic data a re important in view of some of the unusual thermal properties of thes e materials.