Abstract
Laser direct writing (LDW) has been used to pattern 90nm thick permalloy (Ni81Fe19) into 1-D and 2-D microstructures with strong shape anisotropy. Sub-nanosecond laser pulses were focused with a 0.75 NA lens to a 1.85μm diameter spot, to achieve a fluence of approximately 350 mJ.cm-2 and ablate the permalloy film. Computer-controlled sample scanning then allowed structures to be defined. Scan speeds were controlled to give 30% overlap between successive laser pulses and reduce the extent of width modulation in the final structures. Continuous magnetic wires that adjoined the rest of the film were fabricated with widths from 650 nm - 6.75μm and magneto-optical measurements showed coercivity reducing across this width range from 47 Oe to 11 Oe. Attempts to fabricate wires narrower than 650nm resulted in discontinuities in the wires and a marked decrease in coercivity. This approach is extremely rapid and was carried out in air, at room temperature and with no chemical processing. The 6-kHz laser pulse repetition rate allowed wire arrays across an area of 4 mm x 0.18 mm to be patterned in 85 s.
Highlights
Patterned magnetic microstructures are used in many applications such as actuators,[1] sensors[2,3,4] and control of magnetic particles[5] or magnetically-labelled cells.[6]
Laser direct writing (LDW) techniques fall into three main categories depending on whether material is removed (LDW-), modified (LDWm) or added (LDW+).[20,21]
We report the use of LDW- to form microscale structures from thin films of the ferromagnetic alloy Ni81Fe19
Summary
Patterned magnetic microstructures are used in many applications such as actuators,[1] sensors[2,3,4] and control of magnetic particles[5] or magnetically-labelled cells.[6]. Laser direct writing (LDW) of magnetic structures A. Allwood1 1Department of Materials Science and Engineering, University of Sheffield, Sheffield, UK 2Karbala Technical Institute, Alfurat Alawsat Technical University, Iraq (Presented 10 November 2017; received 1 October 2017; accepted 5 December 2017; published online 16 January 2018)
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