Domain Wall Dynamics In Microwires Research Articles

Features of Amorphous Microwires With Spontaneous and Induced Magnetic Bistability

We demonstrate that in Co-rich amorphous microwires with vanishing magnetostriction coefficient, a conventional annealing is quite an efficient method for tailoring of magnetic properties. We observed induced magnetic bistability allowing the observation of fast domain-wall (DW) propagation and giant magnetoimpedance effect simultaneously in the same sample. Moreover, DW dynamics in microwires with induced magnetic bistability presents unusual dependence on applied stress, exhibiting a subsequent growth of DW velocity. For interpretation of these observed changes of hysteresis loops by annealing, we consider stress dependence of the magnetostriction.

Manipulation of Magnetic Properties and Domain Wall Dynamics in Amorphous Ferromagnetic Microwires by Annealing under Applied Stress

The effect of annealing under applied stress on magnetic properties of Co-based or CoFeNi-based glass-coated microwires was studied. It was found that CoFeNi-based microwires became bistable after annealing because of changing of magnetostriction constant sign, while Co-based microwires keep S-shape of hysteresis loop. The domain wall dynamics of microwires which became bistable was also investigated and it was shown that microwires with acquired bistability are more suitable for applications.

Manipulation of domain wall dynamics in microwires by transverse magnetic field

In this paper we studied effect of transversal magnetic field, magnetoelastic anisotropy and defects on DW dynamics of amorphous microwires. We observed that the viscous single DW region is limited by the samples defects, which determine the threshold between single and multiple domain wall propagation regimes.

Fast magnetization switching in Fe-rich amorphous microwires: Effect of magnetoelastic anisotropy and role of defects

We studied effect of magnetoelastic anisotropy and role of defects on domain wall (DW) dynamics and remagnetization process of magnetically-bistable Fe-rich microwires. We manipulated the magnetoelastic anisotropy applying the tensile stresses. Application of stresses resulted in decrease of the DW velocity v, and DW mobility S. Consequently, we observed certain correlation between the magnetoelastic energy and DW dynamics in microwires: decreasing the magnetoelastic energy, Kme, DW velocity can be increased. We are trying to reveal contribution of local defects on DW propagation in amorphous microwires. Below some critical magnetic field, Hn, determined by the microwires inhomogeneities, almost linear DW velocity, v on magnetic field, H, dependence is found. When the applied magnetic field exceeds Hn, new reverse domains can be nucleated and consequently tandem remagnetization mechanism can be realized. The role of defects existing in magnetically bistable microwires is related with nucleation of new reversed domains. Abrupt jumps on v(H) dependences correlate with defects existing in microwires. Magnetic field value, corresponding to such jump on v(H) dependences, correlates with the minimum nucleation field, which determines threshold between single and multiple domain wall propagation regimes. In the latter case, under the action of the magnetic field, a new domain can be spontaneously nucleated in front of the propagating head-to-head closure domain. In this way real structure of microwires limits single DW propagation regime.

Manipulation of domain wall dynamics in amorphous microwires through the magnetoelastic anisotropy

We studied the effect of magnetoelastic anisotropy on domain wall (DW) dynamics and remagnetization process of magnetically bistable Fe-Co-rich microwires with metallic nucleus diameters (from 1.4 to 22 μm). We manipulated the magnetoelastic anisotropy applying the tensile stresses and changing the magnetostriction constant and strength of the internal stresses. Microwires of the same composition of metallic nucleus but with different geometries exhibit different magnetic field dependence of DW velocity with different slopes. Application of stresses resulted in decrease of the DW velocity, v, and DW mobility, S. Quite fast DW propagation (v until 2,500 m/s at H about 30 A/m) has been observed in low magnetostrictive magnetically bistable Co56Fe8Ni10Si10B16 microwires. Consequently, we observed certain correlation between the magnetoelastic energy and DW dynamics in microwires: decreasing the magnetoelastic energy, Kme, DW velocity increases.

Controlling the Domain Wall Dynamics by Induced Anisotropies

Amorphous glass-coated microwires are magnetic materials well-known by very high domain wall velocities reaching up to 15 km/s. In the previous works was shown, that domain wall dynamics in microwires could be effectively tuned by biasing of additional anisotropies. Here we show the possibility of inducing anisotropy to the microwires. Thermal annealing at 300 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$^{\circ}{\rm C}$</tex></formula> in perpendicular field speeds-up domain wall velocity from 1 km/s (as-cast state) to 6 km/s. On the other side, thermal annealing at the same temperature but without perpendicular field leads to the maximum domain wall velocity of about 4 km/s only. This underlines the importance of two perpendicular anisotropies on fast domain wall velocities in microwires.