Effect of synthesis on structure, oxygen voids, valence bands, forbidden band gap and magnetic domain configuration of La2CoMnO6

Abstract

La2CoMnO6 were prepared by the solid state reaction (SSR) and the sol-gel method (SGM). Compared to SSR, the SGM sample has a smaller lattice. The XPS spectra of O 1s core level of SGM show an extra peak at 533.16 eV, owing to the oxygen deficient region. The valence band of SGM moves to the low energy side by 0.36 eV, compared to that of SSR due to the holes generated by oxygen voids. The forbidden band gap energies are 1.78 eV and 1.93 eV for the SGM and the SSR samples, respectively. At low temperature, both the samples have multiple magnetic phases. Both of them have one ferromagnetic (FM) transition at 153 K and one antiferromagnetic (AFM) transition at 123 K in common, and a spin glass state below 75 K is confirmed. Furthermore, SSR has one extra FM transition at 223 K, while SGM does not have. A magnetic configuration as … spin glass↓ - ↓AFM↓- ↑FM↑- ↓AFM↓- spin glass↓ … is proposed to interpret the magnetic properties. The existence of the AFM clusters and the coupling between the AFM cluster and the FM or the spin glass domains are confirmed by the low magnetization at 70 kOe, the high coercive field of over 10 kOe, and the existence of the magnetic exchange bias.