On the Mechanism of the Spin State Transition of (Pr1-ySmy)1-xCaxCoO3

The Ce$_{3-x}$Mg$_x$Co$_{9}$ system evolves from a Pauli paramagnetic ground state for $x = 0$ to a ferromagnetic ground state for $x\approx0.80$ in single phase, polycrystalline samples [Phys. Rev. Applied 9, 024023 (2018)]. In order to better understand this behavior, single crystalline samples of Ce$_{3-x}$Mg$_x$Co$_{9}$ for \textit{x} = 0.01, 0.16, 0.24, 0.35, 0.43 and 0.50 were grown using the flux growth technique, and electrical transport and magnetic properties were s...

The electronic structure of the perovskite La$_{1-x}$Sr$_x$CoO$_3$ has been obtained as a function of Sr substitution and volume from a series of generalized-gradient-corrected, full-potential, spin-density-functional band structure calculations. The energetics of different spin configurations are estimated using the fixed-spin-moment (FSM) method. From the total energy vs spin magnetic moment curve for LaCoO$_3$ the ground state is found to be nonmagnetic with the Co ions in...

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 ($...

Magnetic and electrical properties of four series of rare earth cobaltates of the formula La0.7-xLnxCa0.3CoO3 with Ln = Pr, Nd, Gd and Dy have been investigated. Compositions close to x = 0.0 contain large ferromagnetic clusters or domains, and show Brillouin-like behaviour of the field-cooled DC magnetization data with fairly high ferromagnetic Tc values, besides low electrical resistivities with near-zero temperature coefficients. The zero-field-cooled data generally show a...

A ferromagnetic insulating (FM-I) state in Pr0.75Ca0.25MnO3 has been studied by neutron scattering experiment and theoretical calculation. The insulating behavior is robust against an external magnetic field, and is ascribed to neither the phase separation between a ferromagnetic metallic (FM-M) phase and a non-ferromagnetic insulating one, nor the charge ordering. We found that the Jahn-Teller type lattice distortion is much weaker than PrMnO3 and the magnetic interaction is...

The Pr(1-x}CaxMnO3 system exhibits a ferromagnetic insulating state for the composition range x<0.25. A metallic ferromagnetic state is never realized because of the low hole concentration and the very small averaged A-site cation radius. In the present study, the nature of the magnetic excitations at low temperature has been investigated by specific heat measurements on a Pr0.8Ca0.2MnO3 single crystal. The decrease of the specific heat under magnetic field is qualitatively c...

The layered perovskite cobaltite RBaCo$_2$O$_{5.5}$ (R: rare-earth elements or Yttrium) exhibits an abrupt temperature-induced metal$-$insulator transition (MIT) and has been attributed to spin-state ordering (SSO) of Co$^{3+}$ ions. Here we investigated the hole doping member of PrBaCo$_2$O$_{5.5+x}$ ($0 \le x \le 0.24$) with multiple techniques. The analysis on crystal and magnetic structures by electron and neutron diffraction confirm the SSO in the insulating phase of und...

A powder X-ray diffraction study, combined with the magnetic susceptibility and electric transport measurements, was performed on a series of LnCoO3 perovskites (Ln = Y, Dy, Gd, Sm, Nd, Pr and La) over a temperature range 100 - 1000 K. A non-standard temperature dependence of the observed thermal expansion was modelled as a sum of three contributions: (1) Weighted sum of lattice expansions of the cobaltite in the diamagnetic low spin state and in the intermediate (IS) or high...

The electric, magnetic, and thermal properties of three perovskite cobaltites with the same 30% hole doping and ferromagnetic ground state were investigated down to very low temperatures. With decreasing size of large cations, the ferromagnetic Curie temperature and spontaneous moments of cobalt are gradually suppressed - $T_C=130$ K, 55 K and 25 K and $m = 0.68 \mu_B$, 0.34 $\mu_B$ and 0.23 $\mu_B$ for Nd$_{0.7}$Sr$_{0.3}$CoO$_3$, Pr$_{0.7}$Ca$_{0.3}$CoO$_3$ and Nd$_{0.7}$Ca...

Crystal structure, thermal and magnetic properties were systematically studied in the Y$_{1-x}$Pr$_x$CrO$_3$ with $0 \leq x \leq 0.3$ compositions. Magnetic susceptibility and specific heat measurements show an increase of the antiferromagnetic transition temperature ($T_N$) as Pr is substituted in the Y sites and notable magnetic features are observed below $T_N$. Strong coupling between magnetic and crystalline parameters is observed in a small range of Pr compositions. A s...