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Abstract:
Polycrystalline CeNiIn4 was prepared by arc-melting of the elements and
subsequent annealing at 970 K in vacuum. EuNiIn4 and EuCuIn4 were
synthesized from the elements by reactions in sealed tantalum tubes.
These indium-rich compounds crystallize with the YNiAl4-type structure
which was refined for EuCuIn4 from single-crystal X-ray diffraction
data: Cmcm, a = 450.04(9), b = 1698.7(4), c = 740.2(2) pm, wR2 = 0.0606,
495 F-2 values, 24 variables. The EuCuIn4 structure is built up from a
complex three-dimensional [Cuing] polyanion (265-279 pm Cu-In and
296-331 pm In-In) in which the europium atoms occupy distorted hexagonal
channels. The Eu-Eu distances within these channels (450 pm) are
significantly shorter than the distances between Eu atoms in neighboring
channels (552 pm). The magnetic properties and the specific heats of the
europium compounds have been investigated. Both europium compounds show
the magnetism of divalent Eu ions and antiferromagnetic ordering at low
temperatures. EuCuIn4 is magnetically ordered via a surprisingly complex
sequence of three transitions.
