Coexistence of Different Short-Range-Ordered Spin Fluctuations inCe1−x(La,Y)xSb

Abstract

Diffuse critical neutron-scattering experiments in ${\mathrm{Ce}}_{1-x}{(\mathrm{L}\mathrm{a},\mathrm{Y})}_x\mathrm{Sb}$ ($x=0.1, 0.2$) reveal a fundamental new fluctuation behavior at the onset of magnetic ordering. Two different kinds of short-range-ordered quasistatic spin fluctuations coexist and strongly influence the order of the transition. The unusual fluctuation behavior is the result of competing bilinear exchange and quadrupolar interactions. A simple mean-field model indicates that the phase transitions are close to a multicritical point.