Magnetization Curves of Fe–Ni (50–50) Single Crystals Ordered by Neutron Irradiation with an Applied Magnetic Field

Abstract

Spherical Fe–Ni (50–50) single crystals were ordered by neutron irradiation at 295°C in the presence of a magnetic field. Magnetization curves and magnetic anisotropy energy measurements demonstrate the very important directional effect of the irradiation magnetic field on the bulk anisotropy of the single crystal. When the magnetic field is applied along a fourfold axis, the bulk magnetic anisotropy is tetragonal with a very large value for K3. When the magnetic field is applied along a three fold axis, the bulk magnetic anisotropy is cubic and the threefold axis becomes an easy axis of magnetization; the magnetization measured along the easy direction reaches saturation with a certain law of approach, while the magnetization measured along the [100] direction reaches saturation immediately. The model proposed by Néel, in which three types of quadratic ordered domains are assumed to be strongly coupled, fits well the experimental results. An electron microscopy image shows the different type of ordered domains and the superlattice spots.

Synthesis of single-phase L10-FeNi magnet powder by nitrogen insertion and topotactic extraction

“…L 1 0 -FeNi is drawing much attention as a magnet free of rare-earth elements. Minute quantities of L 1 0 -FeNi are contained in iron meteorites 2,3 , and although it is comprised of common elements such as Fe and Ni, it has high uniaxial magnetic anisotropy (>1 × 10 6  J/m 3 ) 4,5 . The saturation magnetic flux density of L 1 0 -FeNi is 1.6 T (154 A∙m 2 /kg), which is comparable to that of Nd-Fe-B.…”

Resonant x-ray diffraction revealing chemical disorder in sputtered L10FeNi on Si(0 0 1)

“…The FeNi L1 0 structure is a stable phase [9,10] but it is rare in nature, only occurring in meteorites, and it is difficult to synthesize due to the low temperature phase boundary. It has been studied in meteoritic samples [10,11,12] and has been synthesized through neutron bombardment (Néel [13] and Pauleve [14]), electron irradiation (Chamberod [15] and Reuter [16]), in thin film form (Kojima and Mizuguchi [8]), through severe plastic deformation (Lee [17]) and recently through a chemical process (Makino [18]). In all of these methods only very small amounts of the phase are produced.…”

Intrinsic magnetic properties of L1 FeNi obtained from meteorite NWA 6259

“…This value falls into the range of K values reported by Kojima et al 7 for artificially grown ordered FeNi films of different Fe/Ni compositions, but it is somewhat less than the value of K 1 ¼ 1.3 MJ/m 3 obtained by Pauleve in neutron-irradiated bulk FeNi. 4 The Pauleve result suggests that the L1 0 composition to obtain optimal magnetic properties in bulk FeNi may lie closer to equiatomic FeNi with fewer Fe antisite defects. 14 While we had anticipated that NWA 6259 would contain all three chemically ordered L1 0 -type variants, the fit systematically drove the volume fraction of the [001] variant to zero.…”