Spin and Dipole Ordering in Ni_2InSbO_6 and Ni_2ScSbO_6 with corundum-related structure

TL;DR

This study investigates the crystal structure, ferroelectricity, and magnetic ordering of Ni2InSbO6 and Ni2ScSbO6, revealing their non-centrosymmetric structure and incommensurate antiferromagnetic helices below 60-76 K.

Contribution

It reports the synthesis and detailed characterization of Ni2InSbO6 and Ni2ScSbO6 with a corundum-related structure, highlighting their ferroelectric and complex magnetic properties as new findings.

Findings

Both compounds are ferroelectric below 1000 K.

They exhibit antiferromagnetic order below 60-76 K.

Magnetic structure involves incommensurate helices with specific propagation vectors.

Abstract

The complex metal oxides Ni2InSbO6 (NISO) and Ni2ScSbO6 (NSSO) have been prepared in form of polycrystalline powders by a solid state reaction route. The crystal structure and magnetic properties of the compounds were investigated using a combination of X-ray and neutron powder diffraction, electron microscopy, calorimetric and magnetic measurements. The compounds adopt a trigonal structure, space group R3, of the corundum related Ni3TeO6 (NTO) type. Only one of the octahedral Ni positions (Ni(2)) of the NTO structure was found to be occupied by In (Sc). NTO has non-centrosymmetric structure and is ferroelectric below 1000 K, dielectric and second harmonic measurements suggest that also NISO and NSSO are correspondingly ferroelectric. Magnetization measurements signified antiferromagnetic ordering below TN=60 K (NSSO) and 76 K (NISO). The magnetic structure is formed by two antiferromagnetically coupled incommensurate helices with the spiral axis along the b-axis and propagation vector k = [0, ky,0] with ky= 0.036(1) (NSSO) and ky= 0.029(1) (NISO). The observed structural and magnetic properties of NISO and NSSO are discussed and compared with those of NTO.