Evolution from helical to collinear ferromagnetic order of the Eu${}^{2+}$ spins in RbEu(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$

Qianhui Xu, Yi Liu, Sijie Hao +10

The ground-state magnetic structures of the Eu${}^{2+}$ spins in recently discovered RbEu(Fe${}_{1-x}$Ni${}_x$)${}_4$As${}_4$ superconductors have been investigated by neutron powder d…