In my thin film samples I have observed stripe like domain pattern measured using magnetic force microscopy. I have seen in literature that such domains are observed in materials with perpendicular magnetic anisotropy. My sample shows magnetocrystalline anisotropy so I am a bit confused as to what I can conclude about my sample. Is it the actual domain image or some artifact ?
Looks very much like stripe domains to me. Is the thickness of the sample similar to the stripe width? That would be another indication. Also, the magnetic in-plane loops should show some characteristics known for stripe domains. Changing the magnetic field history should change the alignment of the stripes in a reproducible way.javascript:
Thank you Piramanayagam for your answer. I will refer to literature on permalloys. ... My films are soft magnetic perovskite oxides and the current pattern attached is of film around 140nm thick. I have observed wider stripes in case of thicker films.. even checkerboard like patterns also appear in annealed films. Can you give suggestions regarding analyzing these patterns using Fast Fourier Transform?
You can read the the nice text book "Magnetic Domains" by A. Hubert and R. Schaefer, Springer (1998). This book has many pictures that resemble that of yours.
Hi Fozia,
Those stripes do look like they may be an artifact of the laser beam defleting off of the end of your tip. Most of the time the laser beam spot on the MFM tip diffracts around the edges of your cantilever and can create interference patterns that look quite like this image. To check, you can adjust the lift height of your MFM pass and see if the domains become broader at higher lift heights, as the higher you are, the greater the distance between the diffracting cantilever and the surface. Also, do you alter the scan angle/ scan direction and still see the patterns in the same place?
I hope this helps.
Jo
yes I have taken the AFM image I am attaching the image. MFM and AFM images do not match at all. I have also taken the FFT through the software which came along with the machine. I have seen in literature that the FFT of stripe like domain pattern should be have dots separated by distance equal to the domain size. In my case I have obtained fringe like FFT pattern (shown below) for the above shown MFM image. This has confused me more..
the above one is the FFT pattern that I have obtained....AFm pattern somehow did not get attached I am attaching it below.
Dear Fozia,
yes you have to check that you have magnetic stripe by changing the lift height and scan direction as proposed by Johanna.
May be you observed weak or strong magnetic stripe domains. It depends on the direction of magnetic anisotropy induced by the deposition process. Magnitude of the anisotropy components also depends on the intrinsic magneto-crystalline anisotropy, stress-strain induced anisotropy, ..
You can find some work on weak stripes in NiFe layers in my profile with Y. Talbi as first author, and much more related to M. Labrune works.
One other simple thing to do is to perform hysteresis curve M(H) with H in the plane.
You should observe the signature of the stripes in non saturated part (linear behavior before saturation).
I hope it will help you.
Philippe
Dear Johanna thank you for your valuable reply. I have taken MFM scans at various heights and found that the pattern still remains the same. However, I have not tried different scan angles. I will give it a try.
Dear Philippe,
I have performed in-plane hysteresis. Can you clarify exactly what signature pattern will appear in non-saturated part? will it be some zigzag kind of pattern?
at least one change of slope
Do not forget de demagnetized with alternative H field before performing MFM picture.
The stripe should be along the H field.
Looks very much like stripe domains to me. Is the thickness of the sample similar to the stripe width? That would be another indication. Also, the magnetic in-plane loops should show some characteristics known for stripe domains. Changing the magnetic field history should change the alignment of the stripes in a reproducible way.javascript:
I think changing the scan angle can clear things up. If the strip directions change as well then it is an artifact.
I measured the width of stripes but it is much larger than the film thickness. Current MFM pattern is of film of thickness 140nm but the stripe width is around 700nm.
See Coission et al, 2009
J. Magnetism and Mag Mat V 321, 806-809 Magnetic properties of FeSiB thin films displaying stripe domains
and
Amos et al 2008
Journal of Applied Physics V 103, 07E732(1-3) Magnetic force microscopy study of magnetic stripe domains in sputter deposited Permalloy thin films
Stripe domain patterns continue to exist at full saturation, and they naturally increase in width with increasing film thickness, following a square-root relation.
Stripes theoretically are responses to any kind of low anisotropy, including magnetocrystalline, and in the latter case are a result of easy axes misalignment with respect to the free surface of the film. The magnetization normal to the surface creates a magnetostatic energy requirement which results in the formation of stripe domains.
If you have partial out of plane magnetizatio, you can obtain straight stripe domains. If it is completely out of plane, you do worm like patterns. Experimental and theoretical aspects of this is described in:
Magnetic anisotropy and evolution of ground state domain structure in bcc Fe81Ni19/Co (001) superlattices R. Brucas, H. Hafermann, I. L. Soroka, D. Iusan, B. Sanyal, M. I. Katsnelson, O. Eriksson, and B. Hjörvarsson, Phys. Rev. B 78, 024421 (2008).
Here the Co drives the moment out of plane, while the FeNi drives it in plane. By adjusting the ratio of the layers, one can tune the stripe domain structure.
Hope this will be of use for you.
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