Magnetic dilution effect and topological phase transitions in (Mn1-xPbx)Bi2Te4

As the first intrinsic antiferromagnetic topological insulator, MnBi2Te4 has provided a material platform to realize various emergent phenomena arising from the interplay of magnetism and band topology. Here, by investigating (Mn1-xPbx)Bi2Te4 ( 0 <= chi <= 0.82) single crystals via the x-ray, electrical transport, magnetometry and neutron measurements, chemical analysis, external pressure, and first-principles calculations, we reveal the magnetic dilution effect on the magnetism and band topology in MnBi2Te4. With increasing chi, both lattice parameters a and c expand linearly by around 2%. All samples undergo the paramagnetic to A-type antiferromagnetic transition with the Ne ' el temperature decreasing lineally from 24 K at chi = 0 to 2Kat chi = 0.82. Our neutron data refinement of the chi = 0.37 sample indicates that the ordered moment is 4.3(1) (mu B)/Mn at 4.85 K and the amount of the Mn-Bi antisites is negligible within the error bars. Isothermal magnetization data reveal a slight decrease of the interlayer plane-plane antiferromagnetic exchange interaction and a monotonic decrease of the magnetic anisotropy due to diluting magnetic ions and enlarging the unit cell. For chi = 0.37, the application of external pressures enhances the interlayer antiferromagnetic coupling, boosting the Ne ' el temperature at a rate of 1.4 K/GPa and the saturation field at a rate of 1.8 T/GPa. Furthermore, our first-principles calculations reveal that the band inversion in the two end materials, MnBi2Te4 and PbBi2Te4, occurs at the Gamma and Z point, respectively, while two gapless points appear at chi = 0.44 and chi = 0.66, suggesting possible topological phase transitions with doping.