Oxygen Isotope Effect on the Spin State Transition in (Pr$_{0.7}$Sm$_{0.3}$)$_{0.7}$Ca$_{0.3}$CoO${_3}$

G. Y. Wang; T. Wu; X. G. Luo; W. Wang; X. H. Chen

doi:10.1103/PhysRevB.73.052404

paper

Oxygen Isotope Effect on the Spin State Transition in (Pr $_{0.7}$ Sm $_{0.3}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$

arXiv:cond-mat/0510499 · doi:10.1103/PhysRevB.73.052404

Abstract

Oxygen isotope substitution is performed in the perovskite cobalt oxide (Pr $_{0.7}$ Sm $_{0.3}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$ which shows a sharp spin state transition from the intermediate spin (IS) state to the low spin (LS) state at a certain temperature. The transition temperature of the spin state up-shifts with the substitution of $^{16} O$ by $^{18}$ O from the resistivity and magnetic susceptibility measurements. The up-shift value is 6.8 K and an oxygen isotope exponent ( $α_{S}$ ) is about -0.8. The large oxygen isotope effect indicates strong electron-phonon coupling in this material. The substitution of $^{16}$ O by $^{18}$ O leads to a decrease in the frequency of phonon and an increase in the effective mass of electron ( $m$ $^{*}$ ), so that the bandwidth W is decreased and the energy difference between the different spin states is increased. This is the reason why the $T_{s}$ is shifted to high temperature with oxygen isotopic exchange.

arXiv comment4 pages, 3 figures

Oxygen Isotope Effect on the Spin State Transition in (Pr $_{0.7}$ Sm $_{0.3}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$

Abstract

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Oxygen Isotope Effect on the Spin State Transition in (Pr0.7​Sm0.3​)0.7​Ca0.3​CoO3​

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Oxygen Isotope Effect on the Spin State Transition in (Pr $_{0.7}$ Sm $_{0.3}$ ) $_{0.7}$ Ca $_{0.3}$ CoO $_{3}$