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Crystal Structure and Magnetic Properties of a new two-dimensional S=1 quantum spin system Ni_5(TeO_3)_4X_2 (X= Cl, Br)

M. Johnsson·K. W. Toernroos·P. Lemmens·P. Millet
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Abstract

Two new transition-metal tellurium oxy-chlorides of the general formula Ni_5(TeO_3)_4X_2 (X=Cl, Br) have been isolated during the investigation of the ternary phase diagram NiO-NiCl2-TeO2. They crystallize in the monoclinic system, space group C2/c, and for the case of Ni_5(TeO_3)_4Cl_2 the unit cell is a=19.5674(2) A, b=5.2457(1) A, c=16.3084(1) A, with beta=125.289(1). The structure is layered and built up of corner connected [Ni_5O_17X_2] entities, made of five nickel(II) octahedra associated by edge and face sharing. The tellurium(IV) atoms are fixed upon the nickel layers. Their lone pairs E and the halogen atoms are packed in a double layer perpendicular to the [010] direction. From the magnetic point of view, this system provides a new 2D S=1 quantum spin system with antiferromagnetic superexchange interaction. The magnetic susceptibility shows anomalies pointing to magnetic ordering phenomena. The observed transition temperatures vary with the interlayer separation.

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M. Johnsson, K. W. Toernroos, P. Lemmens, P. Millet. 2003-01-20. Crystal Structure and Magnetic Properties of a new two-dimensional S=1 quantum spin system Ni_5(TeO_3)_4X_2 (X= Cl, Br). https://arxiv.org/abs/cond-mat/0301359

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