Magneto-Structural coupling in compressed Manganese Oxide

Transition metal oxides are relevant systems for the earth sciences as these are ideal model systems for Earth's interior. In these systems, pressure increases the magnetic transition temperature, up to a point, where magnetic quenching is predicted. MnO orders magnetically at 118 K in a type II antiferromagnetic structure. This magnetic transition is accompanied by a first order structural transition, from the high temperature cubic paramagnetic phase to a low temperature rhombohedral structure [1], and is well correlated with the magnetic ordering [2]. Interestingly, although magnetic ordering at room temperature is expected only at 60 GPa, a sharp anomaly in the resistivity data has been detected below 10 GPa [3]. Here we present recent results at SNAP at the SNS where high-pressure low-temperature neutron powder diffraction data were collected up to 10 GPa. These data allow determination of the increase of Tc with pressure and characterize the strength of the magneto-structural coupling in MnO when magnetic ordering is induced by pressure.\\[4pt] [1] Tombs NC, Rooksby HP, Nature 165(4194): 442-443 (1950)\\[0pt] [2] Kantor AP, et.al, J. Alloys and Comp. : 402(1-2): 42-45 (2005) \\[0pt] [3] Minomura S. and Drickamer H. G. J. App. Phys. 34, 3043 (1963)