Interplay between charge, orbital, and magnetic ordering in La1-xSrxMnO3 -: art. no. 144414

The evolution with x of the complex phase diagram below 310 K of La1-xSrxMnO3 in the range 0 less than or equal tox less than or equal to0.35 has been mapped out with measurements on a series of melt-grown samples of resistivity rho (T), specific heat C-p(T), magnetization M(T) in applied magnetic fields H= 20 Oe, 5 kOe, and magnetization at 5 K up to 50 kOe. Between the canted-spin anti ferromagnetic insulator and ferromagnetic metal (FM) phases, an unusual interplay between charge, orbital, and magnetic ordering is revealed. In the paramagnetic range T-c < T< T-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-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-oo<T <T-c, the system is conductive and a spin glass in an applied magnetic field H=20 Oe is transformed by H = 5 kOe into a ferromagnetic vibronic phase. As the cooperative orbital-ordering temperature T-JT decreases with increasing x, the transition at T-JT changes from second-order to first-order. In H=50 kOe at 5 K, the magnetization of the Fl phase exceeds the theoretical spin-only value of (4-x)mu (B)/Mn, reaching 4.4 mu (B)/Mn at x=0.15; the magnetization of the FM phase has the spin-only value.