Magnetic properties and magnetic states in La0.9Sr0.1MnO3

Magnetic properties of La0.9Sr0.1MnO3 samples prepared by the floating-zone technique have been studied. The compound possesses different crystal structures at different temperatures T: a pseudo-cubic O "-type structure below 100 K, an orthorhombic O'-type between 100 and 320-340 K and a pseudo-cubic O-type structure above 340 K. Below 145 K a ferromagnetically ordered state is observed. At low temperatures (similar to 4 K) the magnetization sigma, coercivity H-c, differential susceptibility chi(0) in small fields H less than or equal to H-c, and the forced susceptibility chi(Delta) in high fields (30-50 kOe) depend on cooling conditions. After zero-held cooling (ZFC), H-c = 290 Oe, chi(0) is much smaller than the shape susceptibility chi(shape), sigma(50 kOe) = 85.5 emu/g, and chi(Delta) = 5 x 10(-5) cm(3)/g. The measurements after held cooling (FC) in 50 kOe yield H-c < 7 Oe, chi(0) = chi(shape). sigma(50 kOe) = 96 emu/g, and chi(Delta) = 2.5 x 10(-5) cm(3)/g. The sample after ZFC is magnetically heterogeneous, while after FC it is nearly homogeneous. In the heterogeneous state, similar to 20% of the sample volume is occupied by small precipitates (estimated to be 10-20 nm in size) having zero spontaneous magnetization. However, the precipitates become ferromagnetic in high fields via a metamagnetic transition. The results are interpreted within the framework of a mixed ferromagnetic-antiferromagnetic ground state model. (C) 2000 Elsevier Science B.V. All rights reserved.