Influence of the elemental composition of the metal phase of the Co-MgF$_2$ and CoFeZr-MgF$_2$ composites on the magnetotransport properties

The physical properties and structure of nanogranular thin-film composites Co$_x$(MgF$_2$)$_{100-x}$ and (Co$_{47}$Fe$_{42}$Zr$_{11}$)$_x$(MgF$_2$)$_{100-x}$ are studied in a wide range of concentrations of the metal phase (14 $\le x$, at.% $\le$ 62 and 15 $\le x$, at.% $\le$ 55). The systems were studied in the initial state and after heat treatment at various temperatures in a vacuum atmosphere up to 350$^\circ$C. The systems under study exhibit magnetoresistive properties. The maximum values of negative magnetoresistance (MR) reach 7% and 3.25%, respectively. Co$_x$(MgF$_2$)$_{100-x}$ composites, in contrast to (CoFeZr)$_x$(MgF$_2$)$_{100-x}$ composites, exhibit positive tunneling magnetoresistance.