Magnetic order in pure LaMnO3 and in Ca-doped single crystals

We present recent mu IR results on a single crystal of pure LaMnO3, showing the existence of two equal amplitude spontaneous muon frequencies below T- N = 139.5 K. The local fields are 0.9510(3) and 0.6290(2) T at T = 0. The l ower frequency site is identified by virtue of the dependence of the freque ncy on the applied field. The magnetic properties of the end member materia l are briefly discussed on the basis of these observations. Zero-field prec essions are also observed in La0.92Ca0.08MnO3 and in La0.85Ca0.15MnO3 singl e crystals. A new magnetic phase appears in both of them between the ordere d low-temperature and the paramagnetic high-temperature phases. (C) 2000 El sevier Science B.V. All rights reserved.