Metastable nanocrystalline A1 phase and coercivity in Fe–Nd alloys

Magnetic properties and magnetic domain structure of bulk glass forming Nd60Al10Fe20Co10 alloy

“…TEM and HRTEM results also prove the presence of some unknown nano-scale phases in the ribbons and BMG of similar systems [2,13,25]. The magnetic properties of the present thick ribbons and bulk samples [13] are indeed similar to Nd-Fe binary alloys [17][18][19][20][21][22][23][24]. Consequently, we suggest that the presence of a SRO structure, which has a similar local structure as the A1 phase in Nd -Fe binary alloys, is responsible for the hard magnetic properties in samples subjected to relatively low quenching rates (ribbons melt-spun at 3 or 6 m/s in the present work).…”

“…Though a lot of work including high resolution transmission electron microscopy (HRTEM) [23,24], TEM [22], neutron diffraction and Mössbauer spectrometry [21] has been done, the composition and the crystal structure of this phase have not been determined exactly, yet. The composition of the A1 phase was reported to be Nd 3 Fe 7 [18], NdFe 1.1 [19], NdFe 4 O [20] or between NdFe 4 and Nd 2 Fe 3 [23,24] by different authors, while the structure was reported to be cubic, tetragonal, or amorphous [18 -24]. The identification of the A1 phase is difficult as it is formed as a nano-scale eutectic structure [22 -24].…”

Cooling rate controlled microstructure and magnetic properties of metastable Fe20Nd80 alloys

“…There are different conflicting reports about the stoichiometry and structure of the Fe-containing A 1 regions [18][19][20]. Givord et al proposed an amorphous structure for the A 1 regions on the basis of neutron diffraction results [18].…”

“…Croat conducted a series of investigations on amorphous and partially crystalline melt-spun Fe-Nd and Fe-Pr alloys and observed a metastable hard magnetic phase with a Curie temperature of 502 K [10,11]. After these observations the eutectic Fe-Nd and Fe-Pr alloys have been extensively studied in order to characterize the structure of the metastable hard magnetic phases [12][13][14][15][16][17][18][19][20]. Despite the numerous studies on binary Fe-Nd alloys, the consistent understanding of the stable equilibrium eutectic phases, the eutectic composition, and the eutectic morphology is still dubious.…”

Structural and Magnetic Properties of As-Cast Fe–Nd Alloys

“…High coercivity (H ci % 8,6 kOe at RT and H ci % 59 kOe at 20 K) in rapidly quenched Nd 40 Fe 60 alloys was reported by Croat [2] [P. 125, 3 P 3161]. The coercive force of the as-cast Nd-rich Nd-Fe alloys is associated with the metastable anisotropic A 1 phase which is formed during crystallization and cooling below the eutectic temperature by decomposition of the Fe-rich regions within the metastable eutectic [4] [P. 215], [5] [P. 5971], [6] [P. L1], [7] [P. 169], [8] [P. 209], [9] [P. 245], [10] [P. L5], [11] [P. 273], [12] [P. 97], [13] [17] [P. 2483] high H ci of the melt-spun Fe-Nd alloys results from the different nonequilibrium hard magnetic phases. The size of the clusters or nanocrystallites in rapidly quenched Fe-Nd alloys is extremely small and its composition analysis was beyond the limits of TEM capacity at the time.…”