Abstract
Creep motion of magnetic domain wall (DW), thermally activated DW dynamics under subthreshold driving forces, is a paradigm to understand the interaction between driven interfaces and applied external forces. Previous investigation has shown that DW in a metallic system interacts differently with current and magnetic field, manifesting itself as different universality classes for the creep motion. In this article, we first review the experimental determination of the universality classes for current- and field-driven DW creeps in a Ta/CoFeB/MgO wire, and then elucidate the underlying factors governing the obtained results. We show that the nature of torque arising from current in association with DW configuration determines universality class for the current-induced creep in this system. We also discuss the correlation between the field-induced DW creep characteristics and structure observed by a transmission electron microscope. The observed results are expected to provide a deeper understanding for physics of DW motion in various magnetic materials.
Highlights
Dynamical behavior of elastic interfaces under the application of forces is a challenging problem in a multitude of physical systems from different branches of science.[1,2,3,4] In this context, magnetic domain wall (DW) motion under the action of forces is a prototypical example for an elastic interface in this field of interest
While different universality classes for current-induced creep between these two systems can be ascribed to a fundamental difference in the nature of torque induced by current, one of the pertinent questions was whether different universality classes for field- and current-induced DW creeps could be observed in metallic systems
Our previous work utilizing Ta/CoFeB/MgO system with ultrathin Ta underlayer provided solution to this disparity, where field-induced DW creep belongs to the random bond (RB) class and current-induced DW creep is characterized by μ = 0.39 ± 0.06.12 In this article, we first review our previous results for field- and current-induced DW creep, and elucidate the factors which play a key role for determination of the universality class in the context of metallic systems
Summary
While different universality classes for current-induced creep between these two systems can be ascribed to a fundamental difference in the nature of torque induced by current, one of the pertinent questions was whether different universality classes for field- and current-induced DW creeps could be observed in metallic systems. Our previous work utilizing Ta/CoFeB/MgO system with ultrathin Ta underlayer provided solution to this disparity, where field-induced DW creep belongs to the RB class and current-induced DW creep is characterized by μ = 0.39 ± 0.06.12 In this article, we first review our previous results for field- and current-induced DW creep, and elucidate the factors which play a key role for determination of the universality class in the context of metallic systems. Our investigations of current- and field-induced DW creeps are expected to shed light on the long-standing question of the determining factors for universality classes for DW creep. The observed characteristics of field-driven DW motion properties are discussed in the light of the structural properties of Ta/CoFeB/MgO thin film
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