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We report thermal-expansion and specific-heat data of the series La 1 - x Ca x CoO 3 for 0 ⩽ x ⩽ 0.3 . For x = 0 the thermal-expansion coefficient α ( T ) features a pronounced maximum around T = 50 K caused by a temperature-dependent spin-state transition from a low-spin state ( S = 0 ) at low temperatures towards a higher spin state of the Co 3 + ions. The partial substitution of the La 3 + ions by divalent Ca 2 + ions causes drastic changes in the macroscopic properties of LaCoO 3 . Around x ≈ 0.125 the large maximum in α ( T ) has completely vanished. With further increasing x three different anomalies develop.

We report thermal-expansion, lattice-constant, and specific-heat data of the series ${\text{La}}_{1\ensuremath{-}x}{A}_{x}{\text{CoO}}_{3}$ for $0\ensuremath{\le}x\ensuremath{\le}0.30$ with $A=\text{Ca}$, Sr, and Ba. For the undoped compound ${\text{LaCoO}}_{3}$, the thermal-expansion coefficient $\ensuremath{\alpha}(T)$ exhibits a pronounced maximum around $T=50\text{ }\text{K}$ caused by a temperature-driven spin-state transition from a low-spin state of the ${\text{Co}}^{3+}$ ions at low temperatures toward a higher spin state at higher temperatures. The partial substitution of the ${\text{La}}^{3+}$ ions by divalent ${\text{Ca}}^{2+}$, ${\text{Sr}}^{2+}$, or ${\text{Ba}}^{2+}$ ions causes drastic changes in the macroscopic properties of ${\text{LaCoO}}_{3}$. The large maximum in $\ensuremath{\alpha}(T)$ is suppressed and completely vanishes for $x\ensuremath{\gtrsim}0.125$. For $A=\text{Ca}$ three different anomalies develop in $\ensuremath{\alpha}(T)$ with further increasing $x$, which are visible in specific-heat data as well. Together with temperature-dependent x-ray data, we identify several phase transitions as a function of the doping concentration $x$ and temperature. From these data we propose an extended phase diagram for ${\text{La}}_{1\ensuremath{-}x}{\text{Ca}}_{x}{\text{CoO}}_{3}$.

We have studied the thermal conductivity $\ensuremath{\kappa}$ on single crystalline samples of the antiferromagnetic monolayer cuprates ${R}_{2}\mathrm{Cu}{\mathrm{O}}_{4}$ with $R=\mathrm{La}$, Pr, Nd, Sm, Eu, and Gd. For a heat current within the $\mathrm{Cu}{\mathrm{O}}_{2}$ planes, i.e., for ${\ensuremath{\kappa}}_{ab}$ we find high-temperature anomalies around $250\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ in all samples. In contrast, the thermal conductivity ${\ensuremath{\kappa}}_{c}$ perpendicular to the $\mathrm{Cu}{\mathrm{O}}_{2}$ planes, which we measured for $R=\mathrm{La}$, Pr, and Gd, shows a conventional temperature dependence as expected for a purely phononic thermal conductivity. This qualitative anisotropy of ${\ensuremath{\kappa}}_{i}$ and the anomalous temperature dependence of ${\ensuremath{\kappa}}_{ab}$ give evidence for a significant magnetic contribution ${\ensuremath{\kappa}}_{\mathrm{mag}}$ to the heat transport within the $\mathrm{Cu}{\mathrm{O}}_{2}$ planes. Our results suggest, that a large magnetic contribution to the heat current is a common feature of single-layer cuprates. We find that ${\ensuremath{\kappa}}_{\mathrm{mag}}$ is hardly affected by structural instabilities, whereas already weak charge carrier doping causes a strong suppression of ${\ensuremath{\kappa}}_{\mathrm{mag}}$.

The crystal and magnetic structure of ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{1+x}\mathrm{Mn}{\mathrm{O}}_{4}$ $(0\ensuremath{\leqslant}x\ensuremath{\leqslant}0.6)$ has been studied by diffraction techniques and high resolution capacitance dilatometry. There is no evidence for a structural phase transition related to octahedron tilting like those found in isostructural cuprates or nickelates, but there are significant structural changes induced by the variation of temperature and doping which we attribute to a rearrangement of the orbital occupation.