Manganese-based permanent magnet materials

Keller, T.; Baker, Ian

doi:10.1016/j.pmatsci.2021.100872

Cited by 35 publications

(29 citation statements)

References 177 publications

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“…Thus, a finer microstructure of -phase eases the formation of the s-phase, where a reduced time and temperature is necessary to complete the transformation. As reported in previous studies [8,16,30,31], this result supports that the s-phase in Mn-Al-C nucleation takes place at the grain boundaries, which are in higher density in finer microstructures. The grain boundary regions show higher energy when compared to the grain interior.…”

Section: Resultssupporting

confidence: 90%

“…The ferromagnetic Mn-Al-C material is known to be difficult to saturate [33], but our SPS and conventional annealed samples show a quasi-saturated magnetization (114 and 112 Am 2 /kg at 14 T, respectively), as they are single phase [3,34]. These values are comparable with previously reported saturation magnetization for Mn-Al-C ribbons [8,35,36].…”

Section: Resultssupporting

confidence: 87%

“…These characteristics are pointed as crucial to use and develop this material system as ''gap magnets'' with performance in between hexaferrites and Nd-Fe-B [5]. The magnetic properties of Mn-Al are related to the tetragonal s-phase (L1 0 type structure), which is the unique ferromagnetic phase of this material system and yields in a theoretical maximum energyproduct of approximately 101 kJ/m 3 [6][7][8]. This phase was successfully produced in various form, e.g.…”

Section: Graphical Abstract Introductionmentioning

confidence: 99%

“…This phase was successfully produced in various form, e.g. powder, bulk, ribbon, particulate, and thin-films [8].…”

Section: Graphical Abstract Introductionmentioning

confidence: 99%

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Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

et al. 2022

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Mn–Al–C is intended to be one of the “gap magnets” with magnetic performance in-between ferrites and Nd-Fe-B. These magnets are based on the metastable ferromagnetic $$\tau$$ τ -phase with L1$$_0$$ 0 structure, which requires well controlled synthesis to prevent the formation of secondary phases, detrimental for magnetic properties. Here, we investigate the formation of $$\tau$$ τ -phase in Mn–Al–C using Spark Plasma Sintering (SPS) and compare with conventional annealing. The effect of SPS parameters (pressure and electric current) on the phase formation is also studied. Single $$\tau$$ τ -phase is obtained for annealing 5 min at $$500~^\circ \hbox {C}$$ 500 ∘ C with SPS. In addition, we show that the initial grain size of the $$\epsilon$$ ϵ -phase is influencing the $$\tau$$ τ -phase transformation and fraction at a given annealing condition, independently of the annealing method used. A faster transformation was observed for smaller initial $$\epsilon$$ ϵ -grains. The samples obtained by SPS showed comparable magnetic properties with the conventional annealed ones, reaching coercivity of 0.18 T and saturation magnetization of 114 Am$$^2$$ 2 /kg in the optimized samples. The similarity in coercivity is related to the microstructure, as we reveal the presence of structure defects like twin boundaries and dislocations in both materials. Graphical abstract

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 87%

Section: Graphical Abstract Introductionmentioning

confidence: 99%

“…This phase was successfully produced in various form, e.g. powder, bulk, ribbon, particulate, and thin-films [8].…”

Section: Graphical Abstract Introductionmentioning

confidence: 99%

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Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

et al. 2022

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“…Manganese is an alloying component in the production of steel, and its oxides are widely used in fertilizers and ceramics and as catalysts. Due to the chemical structure and physical properties of manganese, its compounds have been intensively studied as promising materials for magnetic, 8–11 luminescence, 12–15 electro-chemical 16,17 and other applications. Particularly, manganese-containing porous materials have attracted much interest as heterogeneous catalysts.…”

Section: Introductionmentioning

confidence: 99%

Sawtooth chains self-assembled from clusters of MnO₆ octahedra within the silicate framework of K₃Mn₄Si₁₀O_24.33(H₂O,OH)₃/V,B

et al. 2022

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Ferromagnetic Mn–Al–C L1₀ Formation by Electric Current Assisted Annealing

et al. 2023

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The ferromagnetic Mn–Al–C τ‐phase ( tetragonal structure) shows intrinsic potential to be developed as a permanent magnet; however, this phase is metastable and is easily decomposed to nonmagnetic stable phases, affecting negatively the magnetic properties. Giving the necessity to careful control of its synthesis, the use of a novel approach is investigated using electric current–assisted annealing to obtain pure τ‐phase samples. The temperature and electrical resistance of the samples are monitored during annealing and it is shown that the change in resistance can be used to probe the phase transformation. Upon increase of electric current density, the required temperature for the ferromagnetic phase formation is reduced, reaching a maximum shift of 140 °C at 45 A mm−2. Even though this noticeable shift is achieved, the magnetic properties are not affected showing coercivity of 0.13 T and magnetization of 90 Am2 kg−1, independently from the electric current density used during annealing. Microstructural investigation reveals the nucleation of the τ‐phase at the grain boundaries of the parent ε‐phase. In addition, the existence of twin boundaries upon nucleation and growth of the metastable phase for all evaluated annealing conditions is observed, resulting in similar extrinsic magnetic properties.

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Manganese-based permanent magnet materials

Cited by 35 publications

References 177 publications

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

Sawtooth chains self-assembled from clusters of MnO₆ octahedra within the silicate framework of K₃Mn₄Si₁₀O_24.33(H₂O,OH)₃/V,B

Ferromagnetic Mn–Al–C L1₀ Formation by Electric Current Assisted Annealing

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Manganese-based permanent magnet materials

Cited by 35 publications

References 177 publications

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

Formation of pure $$\tau$$-phase in Mn–Al–C by fast annealing using spark plasma sintering

Sawtooth chains self-assembled from clusters of MnO6 octahedra within the silicate framework of K3Mn4Si10O24.33(H2O,OH)3/V,B

Ferromagnetic Mn–Al–C L10 Formation by Electric Current Assisted Annealing

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Sawtooth chains self-assembled from clusters of MnO₆ octahedra within the silicate framework of K₃Mn₄Si₁₀O_24.33(H₂O,OH)₃/V,B

Ferromagnetic Mn–Al–C L1₀ Formation by Electric Current Assisted Annealing