Effects of severe shear strain and hydrostatic compression on the crystal structure and magnetism and of manganese oxide Mn3O4

Abstract

The effects of severe shear strain and hydrostatic compression on the magnetostructural correlation of manganese oxide Mn3O4 were investigated using magnetic measurements and x-ray diffraction analyses. Hydrostatic pressures up to PHP = 4 GPa were applied using a diamond anvil cell, whereas shear stress was applied through high-pressure torsion (HPT) processing at PHPT = 6 GPa. A correlation between the coercive field and Jahn–Teller distortion was observed. Hysteresis measurements for magnetization showed a sharp reduction in the coercive field starting from PHP = 2 GPa under hydrostatic pressure. By contrast, an increase of 40% was observed after one rotation (N = 1) during HPT processing. The Jahn–Teller effect was evaluated with the ratio of the long to short distances of the MnO6 octahedron, which remained constant at 1.24 up to PHP = 2 GPa and then increased to 1.26 at PHP = 3 GPa. However, under HPT processing, this ratio changed from 1.24 to 1.27 at N = 1 and decreased to 1.18 at N = 3. The Mn2+–O–Mn3+ bonding angle also changed according to the Jahn–Teller distortion in both compression modes. Thus, the local symmetry of the MnO6 octahedron and MnO4 tetrahedron was modified through compression and subsequent shear stress, allowing for control over the hysteresis of magnetization.