Interplay between charge, orbital, and magnetic ordering inLa1−xSrxMnO3

The evolution with x of the complex phase diagram below 310 K of ${\mathrm{La}}_{1-x}{\mathrm{Sr}}_x{\mathrm{MnO}}_3$ in the range $0<~x<~0.35$ has been mapped out with measurements on a series of melt-grown samples of resistivity $\rho \mathrm{}\left(T\right),$ specific heat $C_p\mathrm{}\left(T\right),$ magnetization $M\left(T\right)\mathrm{}$ in applied magnetic fields $H=20\mathrm{}\mathrm{Oe},$ 5 kOe, and magnetization at 5 K up to 50 kOe. Between the canted-spin antiferromagnetic insulator and ferromagnetic metal (FM) phases, an unusual interplay between charge, orbital, and magnetic ordering is revealed. In the paramagnetic range $T_c<T<\mathrm{}{T}_{\mathrm{JT}}$ the electrons of e-orbital parentage are preferentially ordered into (001) planes and the system exhibits a colossal magnetoresistance. At temperatures below a $T_{\mathrm{oo}}<T_c,$ a different orbital order is found; in an applied magnetic field it is associated with a ferromagnetic insulator (FI) phase. In a narrow temperature interval $T_{\mathrm{oo}}<T<\mathrm{}{T}_c,$ the system is conductive and a spin glass in an applied magnetic field $H=20\mathrm{}\mathrm{Oe}$ is transformed by $H=5\mathrm{}\mathrm{kOe}$ into a ferromagnetic vibronic phase. As the cooperative orbital-ordering temperature $T_{\mathrm{JT}}$ decreases with increasing x, the transition at $T_{\mathrm{JT}}$ changes from second-order to first-order. In $H=50\mathrm{}\mathrm{kOe}$ at 5 K, the magnetization of the FI phase exceeds the theoretical spin-only value of $\left(4\mathrm{}-x\right){\mu }_B/\mathrm{Mn},$ reaching $4.4{\mu }_B/\mathrm{Mn}$ at $x=0.15;$ the magnetization of the FM phase has the spin-only value.