Canted Antiferromagnetism in an Organo-modified Layered Nickel Phyllosilicate

The hydrothermal reaction of 3-aminopropyltriethoxysilane (APTES) and nickel acetate tetrahydrate at 170 °C results in a layered nickel silicate, Ni 3 Si(C 3 H 6 NH 3 )F 0.65 O 1.9 (OH) 4.45 (CH 3 COO) 1.1 · x H 2 O, x = 0.38, with an interlayer spacing of 21 Å. The molecular structure is deduced from powder X-ray diffraction, transmission electron microscopy, X-ray absorption and IR spectroscopies, and a structure is proposed. The structure consists of edge-sharing Ni(O,OH) 6 layers separated by aminopropyl silicate and acetate. The magnetic behavior is described by layers of ferromagnetically coupled nickel ions ( C = 1.28 emu·K·mol - 1 and θ = +35 K) coupled antiferromagnetically at a Néel temperature of 21 K. A small spontaneous magnetization is observed due to canting of the sublattice magnetizations amounting to 0.7°. Isothermal magnetization measurements at 2 K on oriented samples reveal that the easy axis is perpendicular to the layers and a spin-flop field is observed at 20 kOe.