X-ray diffraction studies of the structure of nanocrystals in Fe73.5Si13.5B9Nb3Cu1 soft magnetic alloys before and after thermomechanical treatment

Structure of Nanocrystals in Finemets with Different Silicon Content and Stress-Induced Magnetic Anisotropy

“…The non-linear background is most probably due to the amorphous matrix surrounding the nanocrystallites in the Fe 87-X Si X B 9 Nb 3 Cu 1 alloy. The phase analysis of the alloy with X = 13.5 has shown that contributions of α-FeSi (bcc), Fe 3 Si (D0 3 ), and amorphous phase (matrix) are comparable (Chernenkov et al, 2010). The number of separate peaks of the Fe 3 Si phase is not enough to obtain the reliable value of the Fe 3 Si fraction, but it is predominant.…”

“…In these papers it has been shown that the crystal lattice is stretched in the direction of load application and is compressed in the transverse direction, the strain and the magnetic anisotropy energy being proportional to the load. Detailed studies of the residual strains have shown that deformations of the bcc lattice of FeSi nanocrystals are not isotropic: extension and compression along the <100> directions are maximum, and in the <111> − are minimum (Chernenkov et al, 2010). Therefore, the formation of a state with transverse magnetic anisotropy in the nanocrystals of the Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1 alloy, which is characterized by the orientation of magnetic moments transverse to the direction of stretching, is due to the negative magnetoelastic coupling that is caused by residual anisotropic lattice deformations of the Fe-Si nanocrystals with a large fraction of the Fe 3 Si phase.…”

Induced magnetic anisotropy features in FeCrSiBNbCu nanocrystalline alloy: Role of stress distribution proven by direct X-ray measurements

“…For many different compositions it was shown that stress annealing typically results in no texturing of the nanocrystal lized material [16,17]. Recently new techniques suitable for the studies of the structure of very brittle nanocrystalline materials without special preparation like spark-cut of the disks from the ribbon [16] or complex composites consisting of several overlapping layers of 5-6 mm long fragments [18] have become available.…”

“…From the position of the (h k l) diffraction peak they estimate d corresponding interplanar distances in the Fe 1Àx Si x nanocrys tal lattice and found that the difference of the (h k l) peaks positions in the directions of parallel and perpendicul ar to the ribbon axis (parallel is a direction of the application of the stress in the case of stress annealing) shows the strain of the nanocrystals in the (h k l) direction. The authors had mentioned in their work [18] that residual structure distortions should be discussed using the elastic deformation tensor, mentioni ng at the same time existing experimental difficulties. In a continua tion of these studies (both [17,18] in a transmission mode) we propose to study the origin of magnetic anisotropy induced by stress annealing using the reflection X-ray Sin 2 w technique applied to single amorpho us ribbon, as opposed to the composite consisting of several overlappi ng layers.…”

“…However, they discussed only one reflection (the (6 2 0) for the Fe 3 Si phase). Chernenkov et al [18] filled the gap by detailed study of the structure of nanocrystalline FeSiNbCu alloy after nanocrystallizati on with or without load in the same ''time-temperature condition s'' using complex composite samples for X-ray diffraction studies in a transmission geometry. From the position of the (h k l) diffraction peak they estimate d corresponding interplanar distances in the Fe 1Àx Si x nanocrys tal lattice and found that the difference of the (h k l) peaks positions in the directions of parallel and perpendicul ar to the ribbon axis (parallel is a direction of the application of the stress in the case of stress annealing) shows the strain of the nanocrystals in the (h k l) direction.…”