Anomalous magnetization in the post- perovskite CaIrO 3 John B. Goodenough, University of Texas at Austin, DMR 0904282 The perovskite (Pv) structure has been believed to be the most stable phase of the ABO 3 oxides under high pressure and the Pv MgSiO 3 is the principal constituent of the Earth’s lower mantle. This view was changed a few years ago after the discovery that Pv MgSiO 3 undergoes a phase transition to the post- perovskite (pPv) structure under 125 GPa and 2500 K, the same conditions seen at the Earth’s lowermost mantle or Dlayer. The finding revived interest on the existing CaIrO 3, which has the pPv structure if it is prepared under high temperature and high pressure. Due to the intrinsic local distortion of the pPv structure, the orbital angular momentum L is not quenched in pPv CaIrO 3 . A Walker-type high pressure module. The post-perovskite crystal structure Magnetization of the pPv CaIrO 3 . Loops correspond to different magnetic fields during cooling down. The coercive point (M=0) cannot be reached under H= ± 9 T.
Transcript
Anomalous magnetization in the post-perovskite CaIrO3 John B. Goodenough, University of Texas at Austin, DMR 0904282
The perovskite (Pv) structure has been believed to be the most stable phase of the ABO3 oxides under high pressure and the Pv MgSiO3 is the principal constituent of the Earth’s lower mantle. This view was changed a few years ago after the discovery that Pv MgSiO3 undergoes a phase transition to the post-perovskite (pPv) structure under 125 GPa and 2500 K, the same conditions seen at the Earth’s lowermost mantle or D layer. The finding revived interest on the existing CaIrO3, which has the pPv structure if it is prepared under high temperature and high pressure. Due to the intrinsic local distortion of the pPv structure, the orbital angular momentum L is not quenched in pPv CaIrO3. Moreover, the spin-orbit coupling in this 5d metal oxide is strong. The competition between the spin-spin interaction and spin-orbit coupling leads to anomalous magnetic properties. These findings are useful for designing hard magnets with extremely high coercive force.
A Walker-type high pressure module.
The post-perovskite crystal structure
Magnetization of the pPv CaIrO3. Loops correspond to different magnetic fields during cooling down. The coercive point (M=0) cannot be reached under H= ± 9 T.
Anomalous magnetization in the post-perovskite CaIrO3 John B. Goodenough, University of Texas at Austin, DMR 0904282
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 geoscience. 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. We have also grown high-quality oxide single crystals. Results from this laboratory and collaboration with other groups led to 12 refereed publications in top Journals during the past one year.
Institut Laue-Langevin (ILL), Grenoble, France where we have collaborated with scientists from Spain and France to determine the new 5H polytype structure of BaIrO3 by using the most brilliant neutron source in the world. The result has been published in Journal of American Chemical Society and highlighted by Chemistry and Crystallography, annual report of ILL 2009.
