Simultaneous metal-insulator and spin-state transitions inPr0.5Ca0.5CoO

Role ofA-site cations in the metal-insulator transition inPr0.5Ca0.5CoOBarón-González1, Frontera2, García-Muñoz3 et al. 2010Phys. Rev. B385600View full textAdd to dashboardCite

“…RESULTS Figure 1 shows the dc resistivity of Pr 0.50 Ca 0.50 CoO 3 measured by the four-probe method at zero field and under an applied field of 9 T in cooling-heating cycles. In accordance with previous works, 14,16,17 ͑T͒ shows a sudden drop ͑on heating͒ at T MI Ϸ 80 K. Above T MI , the electrical resistivity is low for a polycrystalline oxide ͑about 1 m⍀ cm͒. This value is very similar to that measured in a single-crystal specimen, 21 and is comparable in magnitude with that found for Pr 0.50 Sr 0.50 CoO 3 and different RBaCo 2 O 5+␦ compounds.…”

“…As reported in previous works, 14,18,19 there is an important contraction of V on cooling across the transition. Spin-state transitions of Co ions are in fact accompanied by perceptible cell volume changes but these changes are driven by changes in Co size ͑deduced from the mean Co-O bond distance͒ induced by the new spin state.…”

“…[14][15][16][17][18][19] Besides, our measurements show that above 100 K, an applied field of 9 T scarcely affects the resistivity and, in fact, slightly enlarges with the field. This demonstrates that the mobility of itinerant electrons does not depend on the magnetic arrangement of the core spins ͑t 2g 5 ͒.…”

“…[14][15][16][17][18][19][20][21][22] This compound presents, on cooling a sudden increase in the resistivity, usually described as a metal to insulator transition ͑MIT͒. It is accompanied by an anisotropic cell anomaly and a sudden large cell volume contraction.…”

Oxygen isotope effect on the spin-state transition in(Pr0.7Sm0.3)0.7Ca0.3CoO3

“…In the study of R 1−x A x CoO 3 (R = Y and variousrare earth elements, A = Ba, Sr, and Ca), Tsubouchi et al 10,11 found an abrupt metal-insulator (M-I) transition and a spin state transition from IS state to LS state at 90 K with decreasing temperature in Pr 0.5 Ca 0.5 CoO 3 , which is accompanied with a decrease of Co-O-Co bond angle. The temperature at which the spin state transition occurs is defined as T S .…”