Single crystal growth, chemical defects, magnetic and transport properties of antiferromagnetic topological insulators (Ge1−δ−xMnx)2<mml:…

To explore new magnetic topological insulators, the authors grew high quality single crystals of (Ge_1-δ-xMnₓ)₂Bi₂Te₅ (GeMn225) (x {≤} 0.47, 0.11 {≤} {δ} {≤} 0.20) by flux and chemical vapor transport methods. Elemental analysis and diffraction data reveal Ge/Bi site mixing and Ge vacancies, with Mn atoms occupying the inner two layers. The x=0.47 sample exhibits bilayer A-type antiferromagnetism with the easy axis along the c-axis below 10.8 K. Compared to MnBi₂Te₄, it shows enhanced effective interlayer AFM exchange and much reduced uniaxial anisotropy. This study highlights the potential of these materials for investigating emergent phenomena, including the layer Hall and quantum metric nonlinear Hall effects.