On the influence of Joule heating induced nanocrystallization on structural and magnetic properties of Co64Fe21B15 alloy

Abstract

Structural and magnetic properties of Joule heated Co64Fe 21B15 alloy have been studied. Crystallization of the specimens starts after Joule heating with 1.6 A current, leading to the formation of nanocrystalline Co80Fe20 phase with grain diameter ranging between 19 and 25 nm. Crystallization of the specimens is found to detoriate the soft magnetic properties. Observed decrease of the hyperfine field of the amorphous component upon Joule heating suggests the increase of the boron near-neighbours to iron and the changes in the hyperfine field of the crystalline component are attributed to the changes in the environment around Fe atom in the specimen. The coercivity is found to obey a domain wall pinning process instead of random anisotropy, as expected in soft magnetic nanocrystalline magnetic materials

Time Dependent Microstructural and Magnetic Properties of Nanocrystalline Fe67.6Co16.9Nb5B8.5P2 Metallic Alloy

“…Perusal of Figure 4 clearly follows the domain wall pinning theory described by Bertotti et al [11]. According to two dimensional wall bowing [12], an explanation was provided on linear relationship between H c and V x D (H c V x D) [11], as is also observed in the present work. Figure 5 depicts the annealing time dependence of lattice parameter, whereas inset shows annealing time dependence of B s .…”

“…After annealing, marginal change were observed in the value of remanance (B r ) and the squareness ratio (B r / B s ) as also reflected in B-H loops. For all annealed specimens, where crystallization process occurs, H c shows considerable increase (shown in the inset of Figure 4), ascribable to increase in anisotropy due to grain growth [2,11,12]. As here H c does not follow Random Anisotropy Model (as H c increases, instead of its reduction), it can be accounted to domain wall pinning on the bcc-Fe nanograins due to local demagnetizing field.…”

Magnetic properties of current-annealed amorphous thin films

“…[4][5][6] Additional systems which have benefit from current annealing include alloys containing largely nonmiscible elements which have been forced in solution by rapid quenching: [7][8][9] in this case, Joule heating allows a finely controlled segregation of the solute atomic species from the hosting matrix, in the form of nanograins or nanoparticles, which could give the systems physical properties not achievable by means of conventional thermal treatments. 10 However, in spite of the large application that current annealing has found in many metallic systems, very few attempts have been done to apply it to thin films.…”