The ordered oxygen deficient `112’ perovskites, LnBaCo₂O_5.50+𝛿 (Ln = lanthanide or Y), exhibit a very flexible structure which can either uptake (𝛿 > 0) or release oxygen (𝛿 < 0) depending on the experimental conditions of synthesis and on the size of the lanthanide. These compounds exhibit remarkably complex magnetic transitions, metal–insulator transition and exceptionally high magnetoresistance. We show herein that their physics is mainly dominated by three different ferromagnetic states, depending on the cobalt valency: FM1 for 𝛿 = 0 (Co³⁺), FM2 for 𝛿 < 0 (Co²⁺/Co³⁺) and FM3 for 𝛿 > 0 (Co³⁺/Co⁴⁺). The competition between ferromagnetism and antiferromagnetism in these phases and the various transitions are discussed taking into consideration the spin state of cobalt, the issue of phase separation and the effect of cobalt coordination and disproportionation.

Polycrystalline diamond coatings are grown on Si (100) substrate by hot filament CVD technique. We investigate here the effect of substrate roughening on the substrate temperature and methane concentration required to maintain high quality, high growth rate and faceted morphology of the diamond coatings. It has been shown that as we increase the substrate roughness from 0.05 𝜇m to 0.91 𝜇m (centre line average or CLA) there is enhancement in deposited film quality (Raman peak intensity ratio of 𝑠𝑝³ to non-𝑠𝑝³ content increases from 1.65 to 7.13) and the substrate temperature can be brought down to 640°C without any additional substrate heating. The coatings grown at adverse conditions for 𝑠𝑝³ deposition has cauliflower morphology with nanocrystalline grains and coatings grown under favourable 𝑠𝑝³ condition gives clear faceted grains.