  The magnetic structures of MnBi2Te4(Bi2Te3)n can be manipulated by tuning the
interlayer coupling via the number of Bi2Te3 spacer layers n, while the
intralayer ferromagnetic (FM) exchange coupling is considered too robust to
control. By applying hydrostatic pressure up to 3.5 GPa, we discover opposite
responses of magnetic properties for n = 1 and 2. MnBi4Te7 stays at A-type
antiferromagnetic (AFM) phase with a decreasing N\'eel temperature and an
increasing saturation field. In sharp contrast, MnBi6Te10 experiences a phase
transition from A-type AFM to a quasi-two-dimensional FM state with a
suppressed saturation field under pressure. First-principles calculations
reveal the essential role of intralayer exchange coupling from lattice
compression in determining these magnetic properties. Such magnetic phase
transition is also observed in 20% Sb-doped MnBi6Te10 due to the in-plane
lattice compression.
