Local and long-range order and the influence of applied magnetic field on single-crystalline NiSb2O6

The magnetic and thermal properties of single-crystalline NiSb2O6 are reported. The Ni2+ ions exhibit local magnetic order below ∼50 K followed by long-range antiferromagnetic order below TN=6.7 K. Analysis of the magnetic susceptibility data using the one-dimensional Heisenberg model with spin S=1 results in a magnetic exchange coupling J||/kB∼26.0(1) K. TN is observed to either increase or decrease depending on whether field is applied perpendicular or parallel to the magnetic moment axis. A two-sublattice magnetic structure, with the axis of alignment alternating by 90∘ between neighboring layers along the crystallographic c axis, is argued to result in two magnetic transition temperatures for certain magnetic field directions, which agrees well with theory. This leads to a highly anisotropic magnetocaloric effect.