Magnetic properties of Fe-doped MnAl

Manchanda, Priyanka; Kashyap, Arti; Shield, Jeffrey E.; Lewis, L. H.; Skomski, Ralph

doi:10.1016/j.jmmm.2014.04.007

Cited by 39 publications

(20 citation statements)

References 31 publications

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“…Nevertheless, the majority of published results about phase transitions in MnAl leading to formation of magnetic phases with good stability were mostly theoretic until recently. Ab initio approaches have given reasons to consider that magnetic ground state of the τ-MnAl is ferromagnetic [ 24 , 25 , 26 ], having a magnetic moment of about 160 emu/g. Density functional theory approaches [ 27 ] showed that large magneto-crystalline anisotropies of about 1 MJ/m 3 can be expected for MnAl and MnGa, together with a saturation magnetization value of about 0.8 MA/m.…”

Section: Introductionmentioning

confidence: 99%

Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

et al. 2021

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Melt spun ribbons of Mn53Al45C2 and Mn52Al46C2 have been synthesized by rapid quenching of the melt with the purpose of monitoring the ε-τ phase transformation to show technologically feasible ways to increase magnetic parameters and to illustrate the viability of these alloys as the next generation of rare earth (RE)-free magnets. By differential scanning calorimetry (DSC), activation energies and temperatures of onset of the ε-τ phase transformation were obtained. Structural analysis was performed using X-ray diffraction (XRD) and the resulting XRD patterns were quantitatively assessed using full profile Rietveld-type analysis. Appropriate annealing was performed in order to enable the ε-τ phase transformation. While hcp ε-phase was found to be predominant in the as-cast samples, after appropriate annealing, the tetragonal τ-phase, the one that furnishes the relevant magnetic response, was found to be predominant with an abundance of about 90%. The data suggested a mechanism of hcp ε-phase decomposition controlled by the segregation towards the interfacial regions, having the rate of transformation governed by antiphase boundary diffusion processes. Magnetic measurements of annealed sample Mn53Al45C2, consisting of predominant tetragonal τ-phase, showed high values of magnetization and increased coercivity, consistent with an energy product of about 10 MGOe, similar with previously reported magnetization measurements, providing further insight into the realization of future class of RE-free low-cost permanent magnets.

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Section: Introductionmentioning

confidence: 99%

Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

et al. 2021

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“…The occurrence of the τ-MnAl phase was argued to be strongly dependent on the stoichiometry of the initial chemical composition, synthesis methods and subsequent thermal treatment. Evidence was brought about with respect to the fact that the phase transformation of Mn-Al from ε-phase to τ-phase is a two-step process [28][29][30]. In many cases, whatever the preparation pathway, mixtures of various phases are observed rather than only single phase.…”

Section: Introductionmentioning

confidence: 99%

Thermal Stability, Blocking Regime and Superparamagnetic Behavior in Mn-Al-C Melt Spun Ribbons

et al. 2021

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Alloys possessing nominal compositions Mn53Al45C2 and Mn52Al46C2 were prepared by the melt spinning method and were subjected to complex structural, morphological and magnetic investigations. As these alloys can exhibit tetragonal L10-type and τ phase, they have good potential as rare earth (RE)—free magnets. It is, therefore, important to monitor the ε–τ phase transformation and the stability and the magnetic features of the tetragonal phase in an entire temperature interval. By using synchrotron X-ray diffraction, it has been proven that the ε–τ phase transformation occurs gradually, with the τ phase becoming predominant only after 450 °C. Moreover, this phase has been proven to be quite stable without any grain growth even at the highest temperature investigated at 800 °C. Low temperature behavior was thoroughly investigated by using a complex combination of major and minor hysteresis loops combined with the zero field cooled-field cooled magnetization protocols (ZFC-FC). Two different regimes, blocking and superparamagnetic, were documented. A spin reorientation transition was proven to occur at 55 K while a maximum magnetization observed in ZFC-FC curves proved that at about 75 K, a transition from ferro to superparamagnetic state occurs. The existence of a blocking regime below 55 K that is characteristic to nanogranular systems with superparamagnetic behavior has shown further development towards obtaining RE-free magnets.

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“…However, the τ-phase MnAl is metastable and is easily decomposed into thermodynamically more stable β-Mn and γ 2 -phases (Al 8 Mn 5 ) 10 , 11 . Addition of carbon at the octahedral interstitial sites (½, ½, 0) have proven to be an effective way of stabilizing the tetragonal structure with an elongation along the c axis 11 , 12 .…”

Section: Introductionmentioning

confidence: 99%

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl

Fang

Cedervall

Hedlund

et al. 2018

Sci Rep

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The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fine powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a flash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4 hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the flash heated samples display high saturation magnetization as well as increased coercivity.

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Magnetic properties of Fe-doped MnAl

Cited by 39 publications

References 31 publications

Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

Magnetism and ε-τ Phase Transformation in MnAl-Based Nanocomposite Magnets

Thermal Stability, Blocking Regime and Superparamagnetic Behavior in Mn-Al-C Melt Spun Ribbons

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl

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