Crystal structure and magnetic properties of Al₁₅Fe₉RE₂ (RE = Gd, Tb) alloy

Al–Fe-rare earth (RE) ternary compounds have attracted much attention due to their excellent magnetic properties. Here, the crystal structure and magnetic properties of Al₁₅Fe₉RE₂ (RE = Gd, Tb) have been focused. Al₁₅Fe₉RE₂ (RE = Gd, Tb) are tetragonal structured crystals with space group I4/mmm (No. 139, tI26). The lattice constants of Al₁₅Fe₉Gd₂ are a = 8.7441(1) Å and c = 5.0507(1) Å, and the lattice constants of Al₁₅Fe₉Tb₂ are a = 8.7333(1) Å and c = 5.0466(1) Å. Under the magnetic field of 50 Oe, the Curie temperatures T_c of Al₁₅Fe₉Gd₂ and Al₁₅Fe₉Tb₂ are 347 K and 314 K, respectively. In a magnetic field of − 8 ~ 8 T at the temperature of 2 K, the maximum magnetic moment, remanence (M_r), coercivity (H_c), (BH)_max and P_H of Al₁₅Fe₉Gd₂ are 0.5 μ_B/f.u., 0.32 μ_B/f.u., 2.19 T, 51.05 MJ/m³ and 81.08 kJ/m³; the maximum magnetic moment of Al₁₅Fe₉Tb₂ is 2.30 μ_B/f.u., M_r is 1.29 μ_B/f.u., H_c is 1.52 T, (BH)_max is 51.40 MJ/m³ and P_H is 303.09 kJ/m³. In addition, their magnetic characteristics show significant differences at 300 K temperature. The results show that Al₁₅Fe₉Tb₂ has the larger magnetic moment, remanent magnetization, (BH)_max and P_H, while Al₁₅Fe₉Gd₂ has the larger coercivity.