Out-of-plane magnetic anisotropy in bulk ilmeniteCoTiO3

Abstract

Structural, electronic, and magnetic properties of bulk ilmenite ${\mathrm{CoTiO}}_{3}$ are analyzed in the framework of density functional theory, using the generalized gradient approximation and Hubbard-corrected approaches. We find that the G-type antiferromagnetic structure, which consists of antiferromagnetically coupled ferromagnetic $ab$ planes, is the ground state of the system, in agreement with experiments. Furthermore, cobalt titanates present two critical temperatures related to the breaking of the inter- and intralayer magnetic ordering. This would result in the individual planes remaining ferromagnetic even at temperatures above the N\'eel temperature. When spin-orbit coupling is included in our calculations, we find an out-of-plane magnetic anisotropy, which can be converted to an in-plane anisotropy with a small doping of electrons corresponding to about 2.5% Ti substitution for Co, consistent with experimental expectations. We thus present a disorder-dependent study of the magnetic anisotropy in bulk ${\text{CoTiO}}_{3}$, which will determine its magnon properties, including topological aspects.