Low-field magnetic properties of LaMnO3+δ with 0.065≤δ≤0.154 Original Research Article

In a weak magnetic field LaMnO3+δ exhibits at δ=0.065 below the paramagnetic-to-ferromagnetic (FM) Curie temperature, TC, a mixed (spin-glass and FM) phase followed by a frustrated FM phase at δ between 0.100 and 0.154. The same behavior is observed in La1−xCaxMnO3 with x between 0 and 0.3. This can be understood by the similar variation of the Mn4+ concentration, c between ≈0.13 and 0.34, in both materials when x or δ is increased. On the other hand, considerable differences are found between these compounds in the values of the magnetic irreversibility, in the dependencies of TC(c) and the magnetic susceptibility, χ(c), as well as in the critical behavior of χ(T) near TC. These differences can be explained by distortions of the cubic perovskite structure, by the reduced lattice disorder and by the more homogeneous hole distribution in LaMnO3+δ than in La1−xCaxMnO3.