Enhanced hard magnetic properties in partially-doped Mn_3−xGd_xGa (x ⩽ 0.03)

The effect of partial (1–3%) rare-earth Gadolinium doping in D0₂₂ Mn₃Ga hard magnet has been investigated in this work. The Mn₃Ga undergoes magnetic transition at T_c ∼ 745 K, which decreases down to T_c∼715 K upon 1% Gd-doping with introduction of mixed Mn valence states, as revealed from XPS study. The hard magnetic behavior of Mn₃Ga has been observed in a wide temperature range (up to T_c). More importantly, the partial Gd-doping significantly enhances the room temperature hard magnetic properties i.e. squareness ratio (m_r/m_s), coercivity (H_c) and energy product (BHmax) from 0.43, 2.73 kOe and 0.39 MGOe (Mn₃Ga) to 0.57, 4.25 kOe and 0.5 MGOe (Mn_2.97Gd_0.03Ga), respectively. The modified Stoner-Wohlfarth model and low-field minor loop analysis reveal the nucleation hardening mechanism for the magnetization reversal. The study proposes the partial rare-earth doping as a new approach to enhance the hard magnetic properties of rare-earth free hard magnets.