MnBi2Te4, Mn(Bi,Sb)2Te4, and MnBi2Te4(Bi2Te3)m (m ≥ 1) are assigned to magnetic topological insulators. Successful application of these materials in nanoelectronic devices calls for comprehensive investigation of their electronic structure and magnetic properties in dependence of the Bi/Sb atomic ratio and the number m of Bi2Te3 blocks. The magnetic properties of the surface of MnBi2Te4, MnBi4Te7, and Mn(Bi Sbx)2Te4 compounds (x = 0.43 and 0.32) have been studied using the magneto-optical Kerr effect. It is shown that the temperatures of magnetic transitions on the surface and in the bulk of MnBi4Te7 and Mn(Bi, Sb)2Te4 differ significantly. [ABSTRACT FROM AUTHOR]