How to set UCF files for two different layers of materials?

[Li Shan]

Hi guys!

I am learning to use UCF file while running the vampire. When I set up two different layers of materials, such as Co/Pt, how can I set different unit cells for these two layers of materials in the UCF file and set their interactions?

If possible, please show me a similar example file.

Thanks.

Shan

[gabo...@gmail.com]

 Working with unit cell file (ucf) multilayers can be challenging.

One limitation that makes that difficult is not being able to specify structure parameters individually (i.e., as two different ucf files).  A single ucf file, as further explain at [1], has to be used with layers needing defined in a common lattice (usually cubic).

The material parameters for each layer are easier to define though.  The Bilayer and Multilayers on the tutorial page at [2] can be helpful.  For latest (6.0) or recent VAMPIRE versions, there is unit-cell-category keyword that can be needed.  More information on that can be found at [3].

Handling the interface between the layers can be strenuous, but a previous user provide some advice for making it easier at [4].

Another significant limitation of VAMPIRE is it not having non-orthogonal lattice types for defining those types of cells. For more about why that is, you may see [5].  You might have seen at [6] the different orthogonal lattice types currently supported by VAMPIRE such as simple cubic (sc).  There is a workaround for a non-orthogonal lattice that a VAMPIRE user pursued that you may read more about at [7].

If you happen to be treating Pt as non-magnetic, then that would make your multilayer calculation easier as you could use the remove or keep keywords.  For more on that, refer to [8] and [9].

[1] https://groups.google.com/g/vampire-users/c/gNw54NFoccw/m/Ws_WwtieHO8J

[2] https://vampire.york.ac.uk/tutorials/

[3] https://groups.google.com/g/vampire-users/c/QGFtYVB6Kd8/m/aJLRijgZBQAJ

[4] https://groups.google.com/g/vampire-users/c/AQn5Tqa0WXA/m/snlqsV-PBgAJ

[5] https://groups.google.com/g/vampire-users/c/ubgiSq3X9AY/m/PgNtvEnECQAJ

[6] https://vampire.york.ac.uk/tutorials/system-generation/crystal-structure/

[7] https://groups.google.com/g/vampire-users/c/FsXzHbAgwcI/m/1vRZa-qvCwAJ

[8] https://groups.google.com/g/vampire-users/c/GUja_vMnRFM/m/97-geUqJAAAJ

[9] https://groups.google.com/g/vampire-users/c/-aPrvN9uqFM/m/3XzqrBe3CAAJ

Kind Regards,

Gavin

VAMPIRE user

[Vinod Naik Bhukya]

Hi all,

Say I have a multilayer repeated stack such as [Pt/Co]3/Pt/CoFeB.....If I consider Pt as non-magnetic and consider only Co and CoFeB, then CoFeB is basically bcc, and Co is actually hcp or if we use fcc....then in this case?

1. can we specify two unit cells for two different materials in the input file?

2. Or we need to write a custom unit cell file and use unit cell category in the material file?

3. Is there any other way?

gabo...@gmail.com 在 2024年5月24日 星期五晚上11:23:30 [UTC+8] 的信中寫道：

[Richard Evans]

Hi,

You can get from BCC to BCT (body-centred tetragonal) which is the same as FCC with the correct c/a ratio, and the usual structure for nanoscale Co. As Gavin mentioned, you need to create a unit cell file for this structure to ensure physically sensible epitaxy and interactions (or just approximate Co as BCC, which is only slightly different from BCT).

Cheers,

Richard

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