On the Mechanism of the Spin State Transition of (Pr_1-ySm_y)_1-xCa_xCoO₃

Abstract

Transport, thermal and magnetic measurements have been carried out on (Pr1-ySmy)1-xCaxCoO3. The system exhibits a structural phase transition accompanied by the spin state change from the intermediate spin (IS) state to the low spin (LS) state with decreasing temperature T. We have constructed a T-y phase diagram for x=0.3 and T-x ones for y=0.2 and 0.3. By analyzing their magnetic susceptibilities, the number of Co ions excited to IS state (or the electron number in the eg orbitals), nIS, are roughly estimated. With increasing y or with decreasing x, nIS decreases, and the phase transition changes gradually to the (IS-LS) crossover-like one. We discuss on the possible role of the Pr atoms in realizing the transition.Comment: 13 pages, 12 figures, Submitted to J. phys. Soc. Jp

Phase diagram and isotope effect in(Pr1−yEuy)0.7Kalinov1, Gorbenko2, Талденков3 et al. 2010Phys. Rev. B144200View full textAdd to dashboardCite

“…In this situation, the partial substitution of R 3+ by a smaller R ′3+ in (R 1−y R ′ y ) 1−x A x CoO 3 systematically increases the chemical pressure, which should enhance the crystal field splitting and therefore stabilize the low-spin state. 17,34 Thus, small changes in the lattice characteristics may critically determine the physical properties of cobaltites.…”

“…However, the data obtained for samples of Pr 0.7 Sr 0.3 CoO 3 [41] and La 0.7 Sr 0.3 CoO 3 [5,42] prepared under normal oxygen pressure show that the expected oxygen deficiency should be about 0.02 − 0.04. The comparison of the transition temperatures for closely related (PrSm) 0.7 Ca 0.3 CoO 3 samples annealed under oxygen pressure of 1 bar [36] and of 60 bar [20,34] suggests that the presumed oxygen deficiency hardly affects the physical properties.…”

Electrical resistivity anomaly in (Pr1−yMy)1−xCaxCoO3 epitaxial films (M=Y, Gd) fabricated by pulsed laser deposition

“…Similar metal-insulator (MI) transition was evidenced also in the less doped Pr 1−x Ca x CoO 3 (x=0.3) under higher hydrostatic pressures and in the (Pr 1−x RE y ) 1−x Ca x CoO 3 system (0.2<x<0.5) with a partial substitution of Pr by smaller RE cations such as Sm, Eu, and Y under ambient pressure. [7][8][9] This peculiar transition appeared to be conditioned not only by the presence of both Pr and Ca ions, but also by a larger structural distortion of the CoO 6 network, depending on the average ionic radius and size mismatch of perovskite A-site ions. 9 Furthermore, the critical temperature T MI was found a corresponding author fujishiro@iwate-u.ac.jp 2158-3226/2016/6(2)/025318/9 6, 025318-1 © Author(s) 2016.…”

Jumps in entropy and magnetic susceptibility at the valence and spin-state transition in a cobalt oxide

“…15 It must be emphasized that the VSST was systematically found to develop in the paramagnetic regime; indications of strong ferromagnetic correlations and possible short-range ordering (likely related to Co 4+ ) were only reported at much lower temperatures (typically at T  5 K). 1,3,8 4 Magnetization measurements were carried out with a superconducting quantum interference device magnetometer (MPMS, Quantum Design). Isothermal magnetization curves at selected temperatures demonstrated that the magnetization (M) varies linearly with the magnetic field (H) for temperature higher than  20 K. Accordingly, an isofield magnetization curve was measured in a field of 1 T and the dc susceptibility  (T > 20 K) was derived from the ratio M/H.…”

“…1,[3][4][5]7,8,13 In a recent x-ray absorption spectroscopy (XAS) study on Pr 0.5 Ca 0.5 CoO 3 , however , Herrero et al showed that the spin state of Co 3+ above T* can be equally well described by an inhomogeneous mixture between low-spin and high-spin (HS, 2 …”