Transport and Magnetic Studies on the Spin State Transition of Pr1-xCaxCoO3 up to High Pressure

Fujita Toshiaki, Miyashita Takeshi, Yasui Yukio, Kobayashi Yoshiaki, Sato Masatoshi, Nishibori Eiji, Sakata Makoto, Shimojo Yutaka, Igawa Naoki, Ishii Yoshinobu, Kakurai Kazuhisa, Adachi Takafumi, Ohishi Yasuo, Takata Masaki

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Transport and magnetic measurements and structural and NMR studies have been carried out on (Pr1-yR/′y)1-xAxCOO3 {R′ = (rare earth elements and Y); A = (Ca, Ba and Sr)} at ambient pressure and high pressure. The system exhibits a phase transition from a nearly metallic to an insulating state with decreasing temperature T, where the low spin (LS) state of Co3+ is suddenly stabilized. For y = 0, we have constructed a T-x phase diagram at various values of the external pressure p. It shows that the (T, x) region of the low temperature phase, which is confined to a very narrow region around x = 0.5 at ambient pressure, expands as p increases. For the occurrence of the transition, both the Pr and Ca atoms seem to be necessary. The intimate relationship between the local structure around the Co ions and the electronic (or spin) state of Co3+ ions is discussed: For the smaller unit cell volume or the smaller volume of the CoO6 octahedra and for the larger tilting angle of the octahedra, the temperature of the transition becomes higher. The role of the carriers introduced by the doping of the A atoms, is also discussed. By analyzing 59Co-NMR spectra and magnetic susceptibility of Pr1-xCaxCoO3, the electronic-energy-separations among the different spin states of Co3+ and Co4+ are roughly estimated.

Original languageEnglish
Pages (from-to)1987-1997
Number of pages11
JournalJournal of the Physical Society of Japan
Issue number7
Publication statusPublished - 2004


  • PrCaCoO
  • hole doping
  • metal-insulator transition
  • spin state change
  • transport and magnetic properties


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