Abstract
Measurements of magnetostriction on a single crystal of antiferro-magnetic nickel oxide were made in fields up to 21 kilo-oersteds. The order of magnitude of the magnetostriction is the same as that for ferromagnetic materials, viz about -20 × 10-6 and a square law relation, with field, is obeyed up to several thousand oersteds before a gradual saturation tends to set in. The dependence of strain on field and measuring directions is described with respect to axes that constitute cylindrical symmetry.