The effect of stress distribution in the bulk of a microwire on the magnetization processes

The Influence of Internal Stress on the Nanocrystal Formation of Amorphous Fe73.8Si13B9.1Cu1Nb3.1 Microwires and Ribbons

“…The obtained distributions of the nucleation frequency and growth rate of the nanocrystals allowed for calculating the distribution of the crystallized volume fraction X over the microwire radius (Figure 6). One can see from Figure 6 that the volume fraction of the formed nanocrystals significantly increased in the near-surface region, where the value of compressive stresses can reach 2 GPa [6,8]. At that region, the average volume fraction of nanocrystals in the microwire, calculated from the distribution in Figure 6, was about 29%.…”

“…where σ(x) = σ rr + σ θθ + σ zz is the sum of diagonal components of a stress tensor of the metallic core of a microwire with respect to the sign, calculated according to [6,8], γ is the effective value of the stress relaxation parameter, obtained from an experiment with the ribbons. ∆V/V is the value of a bulk effect calculated from the difference between densities of amorphous material and formed nanocrystals:…”

“…The growth rate for the ribbon was 2.23•10 −11 m/s, assuming that only the bulk effect was presented and σ(x) = 0 in (3). By using the stress distribution σ(x) as a function of the distance to the microwire axis calculated according to [6,8], as well as expression (2), the distribution uc(x) was calculated (Figure 4). The obtained values of nanocrystal growth rate were within the range of 2.22•10 −11 -2.30•10 −11 m/s.…”

“…Despite shell removing, the character of the total stress distribution does not change (strong compressive stress on the surface part and weak tensile stress in the central part). This difference in the stress state not only affects the magnetization reversal process and the shape of a hysteresis loop [7,8] but it should also affect the processes of crystal formation at the initial stages. Previously, the effect of mechanical stresses on the crystallization and magnetic properties of Co-rich microwires was observed in [9][10][11].…”