By combining the results of magnetization, resistivity, and neutron powder-diffraction data for stoichiometric ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3,$ we have constructed a phase diagram that describes the magnetic, transport, and structural properties and the relationships among them as a function of composition $(0.1\mathrm{}<~x<~0.2)$ and temperature (10–340 K). We show that, with increasing Sr content, the Curie temperature increases linearly, while the temperature of an orbital ordering transition to a state with a large coherent Jahn-Teller (JT) distortion decreases. These two phase-transition lines cross at $x=0.145\mathrm{}$ and $T=210\mathrm{}\mathrm{K}.$ When the transition to the ferromagnetic state occurs in a phase that has a large coherent JT distortion $\mathrm{}(x<\mathrm{}0.145\mathrm{}),$ a strong magnetolattice coupling is observed; the coherent JT distortion is dramatically reduced and the incoherent distortion is enhanced in the ferromagnetic phase. For $x>\mathrm{}0.145,$ where the coherent JT distortion is small above Curie temperature, magnetolattice coupling reduces the incoherent distortion at $T_C$ and strongly suppresses the transition to a phase with a large coherent JT distortion. These observations are consistent with a competition between ferromagnetism and JT distortion that is mediated by a colossal spin-charge-lattice coupling. A metallic state occurs below the Curie temperature when both coherent and incoherent JT distortions are suppressed.

Magnetization of polycrystalline ${\mathrm{La}}_{\text{1−x}}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ samples with $\text{x=0.13}$ and $\text{x=0.16}$ has been measured as a function of temperature and external magnetic field. Using the gathered data and the thermodynamic Maxwell’s relation, changes of the magnetic contribution to entropy under influence of the magnetic field, allowing to estimate the value of magnetocaloric effect, have been determined. The changes reach ∼7 J/(kg K) in the field of 7 T, which makes the studied samples good candidates for application for magnetic refrigeration. Expressions describing entropy and its change under influence of magnetic field have been derived in the molecular field approximation. Satisfactory agreement between the theoretical curves and the experimental dependencies has been found.

The in-plane magnetic penetration depth ${\lambda }_{ab}$ of the iron selenide superconductor with the nominal composition ${\text{FeSe}}_{0.85}$ was studied by means of muon-spin rotation. The measurements of ${\lambda }_{ab}^{-2}\left(T\right)$ are inconsistent with a simple isotropic $s$-wave type of the order parameter but are rather in favor of two-gap $\left(s+s\right)$ and anisotropic $s$-wave order parameter symmetries, thus implying that the superconducting energy gap in ${\text{FeSe}}_{0.85}$ contains no nodes.

We report measurements of the in-plane magnetic penetration depth $\lambda$ in single crystals of ${\text{SmFeAsO}}_{1-x}{\text{F}}_y$ $\left(x\simeq y\simeq 0.2\right)$ with $T_c\simeq 44\text{K}$. We find that at low temperature $\lambda$ has an exponential temperature dependence which suggests that the Fermi surface is fully gapped. The magnitude of the minimum energy gap, ${\Delta }_1=1.1\pm 0.1k_B{T}_c$ at $T=0$, is significantly smaller than the BCS weak-coupling value suggesting that the gap is either strongly anisotropic or varies significantly between the different Fermi-surface sheets. Our data are well fitted by a two-gap model with the larger gap $\left({\Delta }_2=1.7\pm 0.2k_B{T}_c\right)$ associated with $\sim 80\%$ of the total superfluid density.