Thin film SmCo magnets for use in electromagnetic microactuators

Abstract

Efficient magnetic microactuators require a deposition and patterning of a permanent magnetic material. A material that can be deposited in the range of up to a couple of 10μm is sputtered SmCo. For the fabrication of magnetic microactuators, alternative substrate materials besides silicon are of great interest. Therefore, alumina-ceramic as well as B270-glass substrates were included in the investigation. A maximum energy product of 90kJ∕m3 was achieved for rather thick layers of 30μm deposited on glass or ceramic substrates. The latter substrates were found to be suitable for the deposition of SmCo layers up to a thickness of 50μm. Furthermore, the SmCo exhibits isotropic magnetic properties, thus a magnetization of the permanent magnetic layer can be performed in plane as well as perpendicular to the film plane. For the patterning of these thick SmCo layers ion beam etching and wet chemical etching were examined. For both methods, the suitability of patterning thick SmCo layers could be demonstrated. For the integration of a SmCo permanent magnet in a magnetic microactuator, the two technologies for deposition and patterning of the SmCo layer had to be combined. Two linear microactuators are presented utilizing different integration methods of the SmCo component as well as direction of magnetization.

Integrated Magnetic MEMS Relays: Status of the Technology

“…A comprehensive work published in 2009 by Arnold reviewed the reported literature on microfabricated permanent magnets [103]. Sputtered [104][105][106], electroplated [91,[107][108][109][110] and pulsed-laser [111][112][113] deposited micromagnets have demonstrated excellent magnetic performance at thicknesses up to 100 µm, whereas powder-based fabrication methods facilitate the manufacture of larger structures (up to 1 mm) but with limited properties [114][115][116]. However, the best micromagnets are conventionally deposited rare earth alloys, whose processing unfortunately presents insurmountable challenges that hinder their viability for integration, such as the need for special substrates and high-temperature annealing treatments [103], and exhibit an inconveniently high corrosion rate [117].…”

Investigation of cellular microstructure and enhanced coercivity in sputtered Sm2(CoCuFeZr)17 film

“…[1][2][3] Among the various known permanent magnets, lots of attention has been paid to Sm(CoCuFeZr) z magnets in bulk as well as film due to their extraordinary magnetic properties such as high Curie temperature, large coercivity, large energy product (BH max ), considerably high uniaxial anisotropy, etc. The reported hard magnetic properties of Sm(CoCuFeZr) z bulk compound is mainly due to the formation of a three phase cellular microstructure consisting of rhombohedral Fe-rich Sm 2 (Co,Fe) 17 cells, surrounded by a Cu-rich Sm(Co,Cu) 5 cell boundary phase, and superimposed with a Zr-rich lamellae phase.…”

Micro-patterning of NdFeB and SmCo magnet films for integration into micro-electro-mechanical-systems

“…9 Budde et al reported an increase in etching rate of SmCo from 0.02 µm/min for dry etching to 12.5µm/min for wet etching. 10 A major concern is whether coercivity is altered during structuring. Budde et al referred to the magnetic properties of the nonpatterned films but not to those of the wet etched films, 10 while Wang et al only gave the magnetic properties of films etched at very low rates.…”

“…10 A major concern is whether coercivity is altered during structuring. Budde et al referred to the magnetic properties of the nonpatterned films but not to those of the wet etched films, 10 while Wang et al only gave the magnetic properties of films etched at very low rates. 9 Lemke et al reported that no significant change was observed in the coercivity of their patterned NdFeB films, which however, had relatively low coercivities to begin with (0.2 T).…”