Synthesis, Crystal Structure, and Magnetic Properties of La4Co3O10+δ(0.00≤δ≤0.30)

Abstract

The effects of nonstoichiometry on the crystal structure, thermal expansion, structural phase transitions, and magnetic properties of La4Co3O10+δ, 0.00≤δ≤0.30, have been investigated between 2 and 1000 K. Rietveld analysis of high resolution powder X-ray diffraction data reveals the crystal structure of La4Co3O10+δ(Ruddlesden–Popper type phase; Lan+1ConO3n+1withn=3) to be slightly monoclinically distorted, space groupC2/m. The monoclinic distortion increases and the unit cell volume decreases slightly on increasing nonstoichiometry,δ. A structural phase transition, monoclinic to tetragonal, possibly via an intermediate orthorhombic state, occurs at 840 K. Magnetic susceptibility data indicate long-range antiferromagnetic ordering belowTN≈13 K. Above 20 K there are three temperature regimes with nearly Curie–Weiss paramagnetic behaviour for the magnetic susceptibility: 20–80 K, 100–450 K, 650–985 K. This indicates a temperature-induced change from a lower, possibly via an intermediate, to a higher spin configuration for CoIIIcomparable to that described for LaCoO3. Field-dependent magnetic susceptibility is observed forδ>0.00 forT<100 K.