We report on structural, magnetic, and electrical properties of Sr-doped ${\mathrm{LaMnO}}_3$ single crystals for doping levels $0.4<~x<~\mathrm{0.85.}$ The complex structural and magnetic phase diagram can only be explained assuming significant contributions from the orbital degrees of freedom. Close to $x=0.6\mathrm{}$ a ferromagnetic metal is followed by an antiferromagnetic metallic phase below 200 K. This antiferromagnetic metallic phase exists in a monoclinic crystallographic structure. Following theoretical predictions this metallic antiferromagnet is expected to reveal an ${(x}^2-y^2)$-type orbital order. For higher Sr concentrations an antiferromagnetic insulator is established below room temperature.

The temperature-dependent Raman spectra of orthorhombic $R\mathrm{Mn}{\mathrm{O}}_3$ $(R=\mathrm{Pr},\mathrm{Nd},\mathrm{Sm},\mathrm{Eu},\mathrm{Gd},\mathrm{Tb},\mathrm{Dy},\mathrm{Ho},\mathrm{Y})$ were studied in the $5–300\mathrm{K}$ temperature range. It was established that while the materials with large $R^{3+}$ ionic radius $r_R$ and $A$-type antiferromagnetic order $(R=\mathrm{Pr},\mathrm{Nd},\mathrm{Sm})$ exhibit significant phonon softening and other anomalies with decreasing temperature near and below $T_N$, the effect of magnetic ordering is much weaker or negligible in compounds with $R=\mathrm{Eu}$, Gd, Tb, Dy, Ho, and Y, characterized by small $r_R$ and incommensurate magnetic structure. The results are discussed accounting for the variations with $r_R$ of the type of magnetic ordering and related spin-phonon interaction.

We report on structural, magnetic, electrical, and thermodynamic properties of Gd-doped $\mathrm{La}\mathrm{Mn}{\mathrm{O}}_3$ single crystals for Gd doping levels $0⩽x⩽1$. At room temperature, for all doping levels the orthorhombic O’ phase is indicative of a strong Jahn-Teller distortion. All compositions are insulating. The magnetism of ${\mathrm{La}}_{1-x}{\mathrm{Gd}}_x\mathrm{Mn}{\mathrm{O}}_3$ is dominated by the relatively strong $\mathrm{Mn}\mathrm{O}\mathrm{Mn}$ superexchange. For increasing Gd doping, the weakening of the nearest-neighbor exchange interactions due to the significant decrease of the $\mathrm{Mn}\mathrm{O}\mathrm{Mn}$ bond angles leads to the continuous suppression of the magnetic phase-transition temperature into the A-type antiferromagnetic low-temperature phase. The temperature dependence of the magnetization can only be explained assuming canting of the manganese spins. The magnetic moments of Gd are weakly antiferromagnetically coupled within the sublattice and are antiferromagnetically coupled to the Mn moments. For intermediate concentrations compensation points are found, below which the spontaneous magnetization becomes negative. In pure $\mathrm{Gd}\mathrm{Mn}{\mathrm{O}}_3$ the Mn spins undergo a transition into a complex, probably incommensurate magnetic structure at $41.5\mathrm{K}$, followed by a further ordering transition at $18–20\mathrm{K}$ revealing weak ferromagnetism due to canting and finally by the onset of magnetic order in the Gd sublattice at $6.5\mathrm{K}$. At the lowest temperatures and low external fields, both magnetic sublattices reveal a canted structure with antiparallel ferromagnetic components.

We present a systematic electron-spin-resonance (ESR) study in single crystals of ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3(0\mathrm{}<~x<~0.2).$ The temperature dependence of the ESR linewidth marks all significant transitions between both orthorhombic ${(O}^{\prime },O)$ and the rhombohedral (R) structural phases of the $T-x$ phase diagram. All significant peculiarities of the ESR spectra for low x values within the $O^{\prime }$ phase can be attributed to the cooperative Jahn-Teller effect on the ${\mathrm{Mn}}^{3+}{e}_g$ states and to the influence of the Dzyaloshinsky-Moriya exchange interaction. Possible relaxation mechanisms at higher doping levels are discussed.

We report on structural, magnetic, dielectric, and thermodynamic properties of ${\mathrm{Eu}}_{1-x}{\mathrm{Y}}_x\mathrm{Mn}{\mathrm{O}}_3$ for Y doping levels $0⩽x<1$. This system resembles the multiferroic perovskite manganites $R\mathrm{Mn}{\mathrm{O}}_3$ (with $R=\mathrm{Gd},\mathrm{Dy},\mathrm{Tb}$) but without the interference of magnetic contributions of the $4f$ ions. In addition, it offers the possibility to continuously tune the influence of the $A$-site ionic radii. For small concentrations $x⩽0.1$ we find a canted antiferromagnetic and paraelectric ground state. For higher concentrations $x⩾0.3$ ferroelectric polarization coexists with the features of a presumably spiral magnetic phase analogous to the observations in $\mathrm{Tb}\mathrm{Mn}{\mathrm{O}}_3$. In the intermediate concentration range around $x\approx 0.2$ a multiferroic scenario is realized combining weak ferroelectricity and weak ferromagnetism, presumably due to a conelike magnetic structure.