The miniaturization of electromagnetic coils offers several benefits, including reduced electrical power requirements for generating desired magnetic fields, increased magnetic field gradients, and compatibility with space-constrained micro-sensor applications. However, at all length scales, generating substantial magnetic field strength relies on effective heat dissipation to mitigate Joule heating. This work introduces microcoils capable of generating static magnetic fields and field gradients exceeding 600 mT and 106 Tm−1, respectively, in a room temperature environment. Such field strengths, previously achievable only with microcoils operating at cryogenic temperatures or in pulsed modes, are realized through an innovative design incorporating radial cuts in an extended planar configuration. This confines the current paths to a small radius, achieving current densities above <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43246_2025_878_Article_IEq1.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="71" /> </InlineMediaObject> <EquationSource Format="TEX">$1.6\times {10}^{12}$</EquationSource> <EquationSource Format="MATHML"><math> <mn>1.6</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mn>12</mn> </mrow> </msup> </math></EquationSource> </InlineEquation> Am−2, by enabling a radial heat flux of <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="43246_2025_878_Article_IEq2.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="71" /> </InlineMediaObject> <EquationSource Format="TEX">$7.8\times {10}^{10}$</EquationSource> <EquationSource Format="MATHML"><math> <mn>7.8</mn> <mo>×</mo> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mn>10</mn> </mrow> </msup> </math></EquationSource> </InlineEquation> Wm−2 through the extended metal structure. The coils’ development was guided by analytical calculations and finite element simulations, and their performance was experimentally validated with lithographically fabricated microcoil devices. Furthermore, these coils demonstrate magnetization reversal of high-aspect-ratio magnetic nanowires with switching fields of several hundred mT, highlighting their potential for magnetic sensor applications, such as switchable magnetic force microscopy probes.

Micron sized coils for the generation of high magnetic fields and field gradients

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2025年7月28日

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Aniruddha Sathyadharma Prasad,
Rachappa Ravishankar,
Bernd Büchner,
Volker Neu,
Thomas Mühl

摘要

The miniaturization of electromagnetic coils offers several benefits, including reduced electrical power requirements for generating desired magnetic fields, increased magnetic field gradients, and compatibility with space-constrained micro-sensor applications. However, at all length scales, generating substantial magnetic field strength relies on effective heat dissipation to mitigate Joule heating. This work introduces microcoils capable of generating static magnetic fields and field gradients exceeding 600 mT and 10⁶ Tm⁻¹, respectively, in a room temperature environment. Such field strengths, previously achievable only with microcoils operating at cryogenic temperatures or in pulsed modes, are realized through an innovative design incorporating radial cuts in an extended planar configuration. This confines the current paths to a small radius, achieving current densities above $1.6\times {10}^{12}$ $1.6 \times 10^{12}$ Am⁻², by enabling a radial heat flux of $7.8\times {10}^{10}$ $7.8 \times 10^{10}$ Wm⁻² through the extended metal structure. The coils’ development was guided by analytical calculations and finite element simulations, and their performance was experimentally validated with lithographically fabricated microcoil devices. Furthermore, these coils demonstrate magnetization reversal of high-aspect-ratio magnetic nanowires with switching fields of several hundred mT, highlighting their potential for magnetic sensor applications, such as switchable magnetic force microscopy probes.