High-pressure synthesis of new oxide Dy 2 Ge 2 O 7 and high-pressure study on crystal and magnetic structures of the perovskite LaCrO 3 John B. Goodenough, University of Texas at Austin, DMR Charges can be separated from an electric dipole, but magnetic monopoles do not exist. The discovery of monopoles from the magnetic excitations in the pyrochlore Dy 2 Ti 2 O 7 has a fundamental impact on science. However, the correlation between magnetic monopoles in Dy 2 Ti 2 O 7 is too weak to host a rich area of physical phenomena like those for strongly correlated electrons. The pyrochlore Dy 2 Ge 2 O 7 has been synthesized successfully under high pressure. The high density of magnetic monopoles in Dy 2 Ge 2 O 7 has allowed us to explore exotic physical properties from strongly correlated magnetic monopoles. The magnetic ordering structure in a crystal is always compatible to the crystal structure. In the perovskite LaCrO 3, pressure induces a first-order orthorhombic to rhombohedral phase transition. However, how the antiferromagnetic spin structure evolves on crossing the phase transition remains unknown. Our in-situ high- pressure neutron diffraction study has revealed that while the Néel temperature changes smoothly on crossing the phase boundary, the easy axis switches relative to an octahedral axis in order to fulfill the symmetry restriction. Dy 2 Ge 2 O 7 LaCrO 3

High-pressure synthesis of new oxide Dy 2 Ge 2 O 7 and high-pressure study on crystal and magnetic structures of the perovskite LaCrO 3 John B. Goodenough, University of Texas at Austin, DMR Education and Outreach. This program provides training to graduate and postdoc students in high-pressure techniques for solid-state reactions and measurements, which is an important subject in areas of solid-state chemistry and physics. Students have also been involved in the development of a state-of-the-art high-pressure facility. The high-pressure facility has a capacity close to 20 GPa. High-pressure synthesis at this pressure level has been rarely seen in material science research. It allows us to explore new compounds and exotic physical properties. We have emphasized the relationship between physical properties and crystal structure of transition-metal oxides. Students also have opportunities to access domestic and international synchrotron and neutron sources to study the crystal structure of samples they have made under high pressure. Results from this laboratory and collaboration with other groups have led to publications in high impact Journals like Physical Review Letters, Nature Communications, and Physical Review B. The D20 beam line in Institut Laue- Langevin (ILL), Grenoble, France offers the most brilliant neutron source in the world, where we have collaborated with scientists from Spain and France to carry out the in-situ high pressure neutron diffraction to determine the temperature- pressure phase diagram of perovskite LaCrO 3 and the change of magnetic structure on crossing the phase transition.