Speaker
Description
The study of the propagation of a single domain wall (DW) is quite important for technological applications in order to understand and improve the operating features of devices based on DW logic. For that purpose, Fe-rich amorphous glass-coated microwires are excellent candidates as their magnetization process consists in the depinning of a single DW that propagates through the microwire at velocities than can be higher than 1 km/s [1]. Many works have been devoted to the dynamic behavior of the DW when an axial magnetic field is applied but only few for applied current [2,3]. In this work we have studied the dynamics of the DW when a pulse of current is applied.
The microwire here studied (Fe$_{75}$Si$_{10}$B$_{15}$, 18.6 $\mu$m of metallic nucleus, 21.6 $\mu$m total diameter and 42 cm length) shows an intrinsic torsion related to their manufacturing process, as a result of which the application of a current induces a change in the longitudinal component of magnetization (inverse Wiedemann effect). Depending on whether the orientation of the circular field is parallel or antiparallel to the $M\phi$ component of the domain, the application of a current to the microwire (constant for the duration of wall propagation) results in an increase or decrease in the velocity of the DW with respect to its value in absence of current (a bias DC magnetic field is applied as well).
Besides, the ability to induce wall movement has been shown under the action of only a current pulse applied to the wire when the pulse magnitude is above a certain threshold value (7.3 mA). The study of the dynamics of the wall has revealed the existence of two propagation regimes, depending on the magnitude of the current pulse, analogously to what has been reported in microwires for the dynamics of the wall within a magnetic field. In particular, for current pulse amplitudes below 10 mA, the velocity shows a dependence on the pulse width that can be described by a power law, corresponding to an intermittent movement of the wall as a consequence of the strong interaction with the defects, so analogous to what occurs in the low axial field regime. For higher amplitudes above 10 mA, the velocity increases linearly with the current, as also happens in the viscous regime of motion induced by axial field.
The mobility obtained in the case of the viscous regime turns out to be approximately 8 times less in the case of current-induced motion than in the case of movement induced by axial field, given the relationship between mobility and component of the magnetization on which the field acts and the preponderance of the anisotropy in the axial direction. Although it is not possible to exactly justify the relationship found between both mobilities (since both the component $M\phi$ as the damping coefficient can be modified as a result of the application of a circular field), it is expected that the mobility associated with the dynamics under axial field is greater than that corresponding to circular field, given the fundamentally axial orientation of the magnetoelastic anisotropy, related with the predominance of tensile stresses in most of the metallic core.
References
[1] H. Chiriac and T. A. Óvári, “Amorphous glass-covered magnetic wires: Preparation, properties, applications,” Progress in Materials Science, vol. 40, no. 5. Elsevier BV, pp. 333–407, Jan. 1996. doi: 10.1016/s0079-6425(97)00001-7.
[2] V. Zhukova, J. M. Blanco, A. Chizhik, M. Ipatov, and A. Zhukov, “Current induced domain wall propagation in Co-rich amorphous microwires,” AIP Advances, vol. 7, no. 5. AIP Publishing, Feb. 23, 2017. doi: 10.1063/1.4977495.
[3] S. Corodeanu, H. Chiriac, A. Damian, N. Lupu, and T.-A. Óvári, “Field and Current Controlled Domain Wall Propagation in Twisted Glass-Coated Magnetic Microwires,” Scientific Reports, vol. 9, no. 1. Springer Science and Business Media LLC, Apr. 10, 2019. doi: 10.1038/s41598-019-42352-1.
