Shear-strain-induced ferromagnetism in antiferromagnetic nickel oxide NiO

The effects of severe shear strain on the magneto-structural correlations in antiferromagnetic nickel oxide (NiO) were investigated using magnetic measurements and x-ray diffraction. The shear strain was applied using high-pressure torsion (HPT) processing under 6 GPa. A ferromagnetic signal appeared in the magnetization curve starting at a number of revolution N = 1. The ferromagnetic signal reached the maximum intensity at N = 2, with a saturation magnetization of 19.5 emu/mol at 5 K. A stronger ferromagnetic moment than that in NiO nanoparticles was observed, indicating the potential of shear strain to modify magnetic properties in antiferromagnetic oxides. After HPT processing, the unit cell volume was reduced, and the inserted strain promoted the appearance of ferromagnetic domains. Thus, HPT processing provides a platform for exploring the strain-induced magnetic behavior of NiO.