Some Introduction of Manganese-based Permanent Magnet

Manganese-based permanent magnet is considered as an option of non-rare earth permanent magnet due to low price. As a special transition metal, Manganese has big unit cell, and atoms occupy four different positions of the unit cell. Ferromagnetism moment will be shown when the interatomic distance of manganese greater than 290 pm, therefore, fabricate Manganese-based alloy with low cost element or introduce interstitial atom to expand the distance of adjacent Manganese atoms is the basic research principle of Manganese-based permanent magnet.

MnAl-based Permanent Magnet Material

MnAl-based alloy have excellent mechanical strength and moderate magnetic performance. The ferromagnetism phase in Mn-Al system is called τ phase which is a metastable phase. M_s Value of τ-Mn₅₀Al₅₀ can reach 40% of Nd₂Fe₁₄B, and magnetic anisotropy value achieves 38 kOe, thus theoretical (BH) _max reached 12.64 MGOe under 5.2 g/cm³. According to Mn-Al binary phase digram, τ phase comes from the solid-state transformation of high temperature ε phase. The τ phase can be obtained by two routes: one is short-time low temperature annealing after got ε parent phase, and the other one is slow cooling from a high temperature. The current research hotspot of MnAl-based permanent magnet mainly around MnAlC.

MnBi Permanent Magnet Material

Low temperature phase MnBi gained many favors rely on its high single uniaxial magnetic anisotropy. The high magnetic anisotropy is originating from the combination of spin-orbit coupling of bismuth’s 5d electron and layered structure of atomic arrangement. Low melting point of bismuth, high vapor pressure and strange peritectic reaction brings the big challenge to the fabrication of pure low temperature phase, then strictly limited commercialization process of MnBi permanent magnet.

MnGa Permanent Magnet Material

Mn-Ga binary phase diagram is comparatively complex, and Mn_xGa_1-x have two main magnetic ordered phases: L1₀ phase and D0₂₂ phase. Research on fabrication of MnGa powder and bulk very few, but application potentiality of MnGa thin film on ultra-high density magnetic recording and spin electronic device has drawn numerous attention in recent years.