Stabilization and Magnetic Properties of T2‐Type MAB Phase Solid Solution W <i> _x </i> Mn _{5− <i>x</i>} SiB ₂

MAB phases represent a promising platform for the synthesis of 2D materials via selective chemical exfoliation, analogous to the well‐known MAX phases. In particular, T2‐type MAB phases offer an attractive route toward rare‐earth‐free magnetic materials by incorporating heavy 5 d elements into the soft ferromagnetic Mn 5 SiB 2 structure. Here, we present a systematic study of the W x Mn 5− x SiB 2 solid solution (0 ≤ x ≤ 1). High‐quality samples were successfully obtained only for x &lt; 0.4. Powder X‐ray diffraction and Rietveld refinement of the x = 0.3 composition confirm the formation of a tetragonal structure (space group I 4/ mcm ), with tungsten showing site preference for the 16 l Wyckoff position. Magnetic measurements on W 0.3 Mn 4.7 SiB 2 reveal robust ferromagnetic ordering with a Curie temperature ( T c ) of 370 K and a large positive Weiss constant ( θ = +406 K), indicative of strong ferromagnetic exchange interactions. The compound exhibits high saturation magnetization of 6.52 μ B /f.u. at 5 K and 4.70 μ B /f.u. at 300 K, along with an open hysteresis loop at room temperature (intrinsic coercivity H c = 2.5 kA m −1 ). These findings highlight the potential of T2‐type layered MAB phases to accommodate heavy 5 d elements while preserving strong ferromagnetic behavior.