Abstract
Domain wall propagation in modulated-diameter cylindrical nanowires is a key phenomenon to be studied with a view to designing three-dimensional magnetic memory devices. This paper presents a theoretical study of transverse domain wall behavior under the influence of a magnetic field within a cylindrical nanowire with diameter modulations. In particular, domain wall pinning close to the diameter modulation was quantified, both numerically, using finite element micromagnetic simulations, and analytically. Qualitative analytical model for gently sloping modulations resulted in a simple scaling law which may be useful to guide nanowire design when analyzing experiments. It shows that the domain wall depinning field value is proportional to the modulation slope.
Highlights
Intensive study is devoted to circular cross-section magnetic nanowires due to their unique fundamental properties and their potential applications in a number of advanced technologies such as data storage, sensing and biomagnetics[1,2,3,4]
The geometry extension into three dimensions and rotational symmetry favors the formation of unconventional magnetic textures which dynamics differs considerably from that studied in two-dimensional flat strips
Diameter modulations of the nanowire synthesized by electrodeposition can be used to control domain wall position by locally reducing its magnetostatic and exchange energy in the smaller cross-sectional parts[20]
Summary
To understand how geometry affects domain wall propagation in a modulated-diameter cylindrical nanowire when a magnetic field is applied, we used our home-made finite element software feeLLGood[24,26]. This curve tends to the Bloch wall parameter value ∆Bloch = 4Aex /μ0Ms2 at R = 027,32. The presence of diameter modulation results in variation of the internal energy of the system depending on the position of the domain wall To estimate the final position of the domain wall and the critical field intensity required to unpin it, we developed the analytical approach presented
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