Destruction of magnetic ordering in “112” LnBaCo2O5.50±δ by calcium doping

The effect of calcium doping upon the magnetic and transport properties of the smaller size lanthanide cobaltites of the type Ln1−xCaxBaCo2O5.50+δ (Ln=Dy and Ho) has been investigated for 0 ≤ x ≤ 0.2 . The substitution of Ln by calcium induces a large deterioration of the long-range magnetic ordering in the system finally leading to a paramagnetic state. Such instability in the magnetic ordering could be related to strong bending of the Co–O–Co bond, the local lattice distortion and the random vacancies in oxygen sublattice. The present results suggest that not only the cobalt valence but also the size of the lanthanide and the local lattice distortion play a crucial role in determining the physical properties of this layered cobaltite.