Nanostructuring of GdFeCo Thin Films for Laser Induced Magnetization Switching

Abstract

The effect of structuring GdFeCo thin films has been investigated in view of laser induced magnetic recording applications. It is found that patterning the substrate via electron beam lithography combined with reactive ion etching before the actual magnetic layer deposition can produce a significant magnetic de-coupling between the obtained structures and their immediate magnetic surrounding. However, upon laser heating, dipolar coupling with this surrounding is found to determine completely the magnetization orientation of the structures, a situation which could be problematic for laser induced recording applications. An alternative structuring approach, based on a lift-off technique of the magnetic layer, is immune to this problem since no magnetic surrounding remains.

Ultrafast heating as a sufficient stimulus for magnetization reversal in a ferrimagnet

“…A polymethylmethacrylate resist is first patterned with an electron beam writer on a glass/Ti(2 nm)/Pt(8 nm) substrate. This pattern is then transferred via lift-off after deposition by magnetron sputtering of the magnetic multilayer AlTi(10 nm)/Si 3 N 4 (5 nm)/Gd 24 Fe 66.6 Co 9.4 (20 nm)/Si 3 N 4 (3 nm), resulting in isolated magnetic structures 23 . Unstructured areas of several 100 µm, quasicontinuous films, and arrays of squares and disks down to 1 µm were fabricated onto the same sample.…”

Highly efficient all-optical switching of magnetization in GdFeCo microstructures by interference-enhanced absorption of light

“…9. The structure and thickness (number between parentheses in nm) of the layers is as follows: glass/Ti(2)/Pt(8)/SiN(5)/GdFeCo(20)/SiN (20).…”

“…This problem can be circumvented by patterning the magnetic films and realizing micro-and nanosized structures. 9,10 However, a thorough understanding of how structuring down to dimensions comparable to or smaller than the optical wavelength affects AOS key parameters, such as switching speed, and fluence threshold, is still lacking.…”

Demonstration of laser induced magnetization reversal in GdFeCo nanostructures

“…These line profiles reveal that a thinning of all the structures occurs at their edges over a distance of 150 nm. The lift-off process, which involves deposition of the magnetic layers on a structured polymer resist, 7 results in thinner edges due to shadowing from the resist during film deposition. As the size of the structure becomes smaller than the shadow, this effect becomes more important to the point that it reduces the thickness of the 100 nm structures by a factor of 2.…”

“…The structuring of this sample in squares and discs with sizes ranging from 2 Â 2 lm 2 down to 100 Â 100 nm 2 has been realized via electron beam lithography in combination with a lift-off process, resulting in isolated magnetic structures. 7 Images of the magnetic domain states in these structures are then obtained using the Elmitec PEEM at the surface/interface: microscopy (SIM) beamline 8 at the Swiss Light Source. A magnetic image is obtained using the XMCD effect at the Fe L 3 edge, the contrast of which is a quantitative measure of the projection of the element specific magnetic moment on the x-ray polarization vector.…”