Multi-k spin ordering in CaFe3Ti4O12 stabilized by spin-orbit coupling and further-neighbor exchange by Patino, MA, Romero, FD, Goto, M, Saito, T, Orlandi, F, Manuel, P, Szabó, A, Kayser, P, Hong, KH, Alharbi, KN, Attfield, JP, Shimakawa, Y