Study of multipolar effects in rare earth and actinide intermetallic compounds by μSR

A review is presented of μSR measurements on CeB6, Ce1-xLaxB6, CeAg, PrCu2, HoB2C2, DyPd3S4 and UPd3 which reveal multipolar, in particular quadrupolar, effects. μ+ Knight shift data imply that the spin polarization of conduction electrons at the μ+ may acquire an unusual temperature dependence and anisotropy in the presence of a non-spherical charge distribution of the f-electrons. This feature is also discussed theoretically. The interplay of dipolar magnetic and electric quadrupolar order is shown to possibly explain properties of the spontaneous fields at the μ+ in the magnetically ordered state, as well as aspects of the μ+ spin lattice relaxation. The possibility of magnetic-octupolar effects is briefly considered