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Contribution of on-site Coulomb repulsion energy to structural, electronic and magnetic properties of SrCoO3 for different space groups: first-principles study

Muhammady S., Sutjahja I. M.

Materials Science Poland

2017

Vol. 35, No. 4

846--856

We report structural, electronic, and magnetic properties of SrCoO3 in Pm3m and P4/mbm space groups, which are calculated by using generalized gradient approximation corrected with on-site Coulomb repulsion U and exchange energies J. The cubic lattice parameter a and local magnetic moments of Co (µCo) are optimized by varying U at Co 3d site. Employing ultrasoft pseudopotential, the values of U = 8 eV and J = 0.75 eV are the best choice for Pm3m space group. We found the value of (µCo) = 2.56 µB, which is consistent with the previous results. It was also found that Co 3d, hybridized with O 2p, is the main contributor to ferromagnetic metallic properties. Besides, norm-conserving pseudopotential promotes a, which is in good agreement with experimental result. However, it is not suitable for P4/mbm space group. By using ultrasoft pseudopotential, the value of U = 3 eV (J = 0.75) is the most suitable for P4/mbm group. Ferromagnetic metallic properties, Jahn-Teller distortion, and reasonable lattice parameters have been obtained. This study shows that U has significant contribution to the calculated properties and also points out that P4/mbm space group with US-PP is suitable to describe experimental results.

Effects of partial Co replacement by Fe in Sr0.775Y0.225CoO3-δ on its magnetic property, oxygen deficiency and crystal structure

Sutjahja I. M., Berthalita F., Mustaqima M., Nugroho A. A., Tjia M. O.

Materials Science Poland

2015

Vol. 33, No. 3

579--587

A study has been conducted on the effects of partial, 10 % Co substitution by Fe in the perovskite Sr0.775Y0.225CoO3-δ compound. The XRD data show that the resulted samples of Fe-free and Fe-doped compounds exhibit good 314 single phase quality with a tetragonal I4/mmm crystal structure. The measured M-T curves display the typical feature of ferromagnetic (FM) transition at 335 K for the Fe-free sample, while showing significantly degraded FM ordering for the 10 % Fe-doped sample. The oxygen deficiency determined from our 10 % Fe doped sample is found to decrease by only 0.025. Further detailed analysis of the XRD data also reveals distinctly different structural changes in the Co–O slabs compared to the 50 % Fe-doped sample which exhibits a complete suppression of FM order. The results of this study, thus, have revealed the close relations among the changes induced by Fe doping in the magnetic ordering of crystal, and its oxygen content as well as the associated local structure in the Co–O layers responsible for the magnetic properties in the compound.