Speaker
Description
The domain structure of amorphous ferromagnetic microwires with positive magnetostriction is formed during production with the Taylor-Ulitovsky method of rapid quenching. The stress distribution results in a large axial domain along the microwire, in which the magnetization takes only two opposite states. There are closure domain structures to minimize magnetostatic energy at the ends of the microwire. The magnetization process occurs by releasing the domain wall (DW) from the closure domain structure, but also by nucleating opposite domains and subsequent movement of the formed DWs, if the external magnetic field is high enough. It has been shown that it is possible to create a single DW in the sample far from the ends, which remains there even after the external magnetic field is turned off.
Recently a new experimental set-up to study the dynamics of a DW moved by an alternating sinusoidal (AC) magnetic field was presented [1] in which the microwire is placed in a system of four coaxial coils. A pair of coils in Helmholtz geometry in parallel or antiparallel combination allows the whole wire to be magnetized axially or a single DW to be created in the place of the local zero field, respectively. If this magnetic field is on, the created DW is in an artificial potential well, and if magnetic field is off the DW is in a local well. The AC magnetic field with angular frequency $\Omega$ generated by the magnetizing coil causes the DW to start oscillating. The voltage induced due to DW oscillation is measured through the pick-up coil. The induced voltage as a function of the angular frequency (from $30$ kHz to $800$ kHz) as well as a function of the amplitude of the alternating field can be measured.
In the present work we study the dynamics of a DW forced to oscillate in a well. Frequency dependences show that the DW in a local well leaves the space inside the pickup coil at relatively low value of amplitudes and frequencies of the applied AC field. The model in which the DW is forced to oscillate in a local parabolic potential well does not describe the observed behavior correctly. The reason may be the large wall axial length to wire diameter ratio [1]. In the case of the artificial potential well, the width of which is larger than the magnetizing coil length, the DW remains inside the magnetizing coil. Along with dynamic measurements, static measurements are also presented, providing information about the local environment in which the domain wall moves.
Acknowledgements
This research was supported by VEGA Grant No. 1/0350/24 from the Scientific Grant Agency of the Ministry for Education of the Slovak Republic.
References
[1] J. Onufer et al., “Dynamics of a single domain wall between axial domains in magnetic microwire,” IEEE Transactions on Magnetics. Institute of Electrical and Electronics Engineers (IEEE), pp. 1–1, 2024. https://doi.org/10.1109/tmag.2024.3481468
