Antiferro-Multipolar Short Range Order above the Antiferro-Quadrupolar Ordering Temperature in CeB_{<b> 6</b>}

Abstract

We have studied the short range order above the long range ordering temperature in CeB 6 and NdB 6 by the measurements of the specific heat and magnetization. The results indicate that both compounds exhibit a large short range order but its nature is quite different, i.e. the antiferro (AF) magnetic fluctuation above the Néel temperature in NdB 6 as is often observed in many of the AF magnets but the unexpected ferromagnetic one is observed above the antiferro-quadrupolar (AFQ) ordering temperature, T Q in CeB 6 . The latter is explained by the coexistence of the AFQ and T x y z AF octupolar short range order above T Q .