Cobalt in strontium titanate as a new off-center magnetic impurity

Abstract

The local structure and oxidation state of the cobalt impurity in SrTiO${}_3$ is studied by X-ray absorption fine structure (XAFS) spectroscopy. The synthesis conditions, under which cobalt predominantly (up to 76%) substitutes the atoms at the $A$ site of the perovskite structure, is found for SrTiO${}_3$(Co) samples. By varying the synthesis conditions, it is possible to appreciably change the ratio between the concentrations of cobalt atoms incorporated into the $A$ and $B$ sites. It is established that the oxidation state of cobalt is +2 at the $A$ site and +3 at the $B$ site. It is revealed that the Co impurity at the $A$ site is off-center, and its displacement from the lattice site is $\sim$1.0 Å. First-principles calculations show that an isolated Co${}^{3+}$ ion at the $B$ site is diamagnetic, whereas the Co${}^{2+}$ ion at the $A$ site is in a high-spin state ($S=3/2$).

7 pages, 4 figures, 3 tables. arXiv admin note: text overlap with arXiv:1912.10711

Cited by in corpus (1)

• On the possibility of incorporation of the iron impurity into $A$ sites in SrTiO${}_3$