Abstract
The perovskite Co oxides Pr1-xCaxCoO3 exhibit at around x∼0.5 an unusual transition at temperature TS [S. Tsubouchi et al. Phys. Rev. B 66, 052418 (2002)PRBMDO0163-182910.1103/PhysRevB.66.052418] with no space group change and no long-range magnetic order. We measured inelastic neutron scattering intensities of magnetic excitations I(Q,ω) for two single crystals of (Pr1-yYy)1-xCaxCoO3 in which the x region of the transition is widened by the Pr-site doping to study whether the recent proposal of the excitonic condensation model is relevant to this "hidden order transition" of the system. While χ′′(Q,ω) seems to have characteristics of strongly correlated Co 3d electrons above TS, it abruptly exhibits a weak feature reminiscent of a pseudogaplike structure at TS with decreasing T. The first peak of the Pr crystal-field excitations has also been observed at low temperatures. Here, using a model of the coexistence of the exciton condensed phase (EC phase) with the nearly or weakly ferromagnetic one, we show that the EC phase appears as the collective transition in Pr1-xCaxCoO3.
Original language | English |
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Article number | 205105 |
Journal | Physical Review B |
Volume | 98 |
Issue number | 20 |
DOIs | |
State | Published - Nov 5 2018 |
Funding
The authors thank Prof. S. Ishihara of Tohoku University and Prof. Y. Ohta and Dr. K. Sugimoto of Chiba University for stimulating discussion. This work was partially supported by JSPS KAKENHI Grant No. JP17K05558. Resources at the High Flux Isotope Reactor, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory were used. Magnetic susceptibility measurements were performed using the SQUID magnetometer (MPMS, Quantum Design) at the CROSS user laboratory.