# Geometry

SLaSi supports a few predefined geometries and can read it from the external file. All sizes are gived in the numbers of the lattice nodes. List of the supported settings:

• circle: a disk with diameter D and thickness h.
• ellipse: ellipsoidal disk with twiced axes a and b, and thickness h.
• rectangle: rectangular parallelotope with sides a and b, and thickness h.
• astroid: astroid with larger size D and thickness h.
• file: reading configuration from file. Needed parameters a, b and h that defined rectangular parallelogram in which the sample will be placed.

Circle with 30 lattice nodes in the diameter and 5 in the thickness can be defined as following:

```geometry = circle
D = 30
h = 5```

Variables geometry, «D», «a», «b» and «h» have no default value.

File with geometry must contains zeros and ones (one number in line) which denotes nodes with nonzero spin. During reading X dimension is changed the most fastest, next is Y dimension and Z. The last parameter for geometry is lattice constant $a_0$, usually defined as

`a0 = 1`

Default value equals 1.

It influences on the strength of the exchange anisotropy, values of the macroscopic magnetic parameters like exchange constant A and rescales lengths.

SLaSi supports consideration of double layer system with different exchange constants and constants of single-ion anisotropy. Position of the interface which lies above the Z node number 5 is defined as

`interface2 = 5`

It has not default value. For defining corresponding material parameters see the Section Magnetic parameters.