Magnetic order in the anhydrous cubic nitrates K3Ce2(NO3)9 and Na3Gd2(NO3)9

Abstract We present measurements of the magnetic susceptibility of K 3 Ce 2 (NO 3 ) 9 and Na 3 Gd 2 (NO 3 ) 9 , cubic systems in which the rare earth sites have axial symmetry about (1 1 1). Paramagnetic resonance results for K 3 Ce 2 (NO 3 ) 9 are also described, which are quite different from those of Ce 2 Mg 3 (NO 3 ) 12 ×24 H 2 O, in which the Ce 3+ ion occupies a nearly identical local environment. Exchange in both compounds is antiferromagnetic in nature. K 3 Ce 2 (NO 3 ) 9 exhibits an antiferromagnetic ordering feature in its susceptibility at T ≈40 mK, while Na 3 Gd 2 (NO 3 ) 9 shows an ordering feature at T ≈200 mK consistent with a ferromagnetic transition.