Figure 4
Hall resistance at different temperatures for [MnGa(t nm)/Co2MnSi]5 superlattice (sample B, t = 4.5 nm). (a) The R Hall curves at different temperatures from 50 to 400 K. Four different magnetic states are depicted (red arrows for Co2MnSi, blue arrows for MnGa), and the transitions between them are indicated by numbers from 1 to 4 for a down-sweep (positive to negative: the green line with arrows). \({H}_{{\rm{C}}}^{-}\) and \({H}_{{\rm{C}}}^{+}\) are the coercive fields of the superlattice as a whole. \({H}_{{\rm{C}}({\rm{MnGa}})}^{+}\) and \({H}_{{\rm{C}}({\rm{MnGa}})}^{-}\) are the coercive fields for the MnGa layers biased by the exchange coupling field from the Co2MnSi layers in the superlattice. (b) The coercivity of the MnGa layers, determined by \({H}_{{\rm{c}}({\rm{MnGa}})}=\,({H}_{{\rm{C}}({\rm{MnGa}})}^{+}-{H}_{{\rm{C}}({\rm{MnGa}})}^{-})/2\). (c) The exchange coupling field \({H}_{{\rm{ex}}}[{H}_{{\rm{ex}}}=({H}_{{\rm{C}}({\rm{MnGa}})}^{+}+{H}_{{\rm{C}}({\rm{MnGa}})}^{-})/2]\) and the coercivity of the superlattices \({H}_{{\rm{c}}({\rm{s}}{\rm{l}})}[{H}_{{\rm{c}}({\rm{s}}{\rm{l}})}=({H}_{{\rm{C}}}^{+}-{H}_{{\rm{C}}}^{-})/2]\) as functions of temperature.
