Issue for `create_sim(mesh)` and `Sim(mesh;driver = "SD")`

[Donghi007]

Dear @ww1g11 ,

I found an issue about creating a random state by usingcreate_sim(mesh) and Sim(mesh;driver = "SD"), respectively.

if I use Sim(mesh;driver = "SD"), like this:

mesh = FDMesh(dx=2e-9, dy=2e-9, dz=2e-9, nx=256, ny=256, nz=53, pbc="xy")
sim = Sim(mesh; driver="SD", name="relax")
init_m0_random(sim)
save_ovf(sim, "save256x256x53_random", type =  Float64)
println("output finished")

The out put ovf file save256x256x53_random.ovf is not correct, it produced a ferromagnetic state not random state.
However, if I use create_sim(mesh) function, like this:

mesh = FDMesh(dx=2e-9, dy=2e-9, dz=2e-9, nx=256, ny=256, nz=53, pbc="xy")
sim = create_sim(mesh)
init_m0_random(sim)
save_ovf(sim, "save256x256x53_random", type =  Float64)
println("output finished")

The output ovf file is correct, a random state created. Similarly, I define a region for example:

#region 1
mesh = FDMesh(dx=2e-9, dy=2e-9, dz=2e-9, nx=256, ny=256, nz=53, pbc="xy")
#sim = Sim(mesh; driver="SD", name="relax")   commend this line
sim = create_sim(mesh)
function initial_layer(i,j,k, dx, dy, dz)    
    if k>3&&k<53-3
        return (0,0,1)
    else
        return (0,0,-1)
    end
end

init_m0(sim, damage_layer_initial)  # Initialize magnetization
save_ovf(sim, "save256x256x53_initial", type =  Float64)

If I use create_sim(mesh) to create this region, this region can be defined correctly. But Sim(mesh;driver = "SD") did not work well.
So, I hope to know what's the different between create_sim() and Sim().

I would be very appreciate for any help you provide :)

[BoyaoLyu]

The magnetization value must be set before initializing the spin because the init_m0_random(sim) function only updates the spin values where $M_s \neq 0$. The Sim function simply creates a structure where Ms is set to 0 everywhere. However, the create_sim function handles this internally by assigning Ms=8e5 value if no value is provided in the arguments.

Try using this:
sim = Sim(mesh) set_Ms(sim, 8e5) init_m0_random(sim)

For the same reason, when applying a spatial initialization, you also need to set Ms in advance.

If you look at the definition of create_sim in src/sim.jl, you'll see that it is just a Sim function with additional initialization steps.

[ww1g11]

Hi @Donghi007,

Thank you so much for reporting this bug! We've just fixed it, and you can install the latest version by running:

add MicroMagnetic#master

If the cluster don't have direct internet access, you can download the ZIP file directly from [this link] and use it to replace the older version.

Best wishes,

[Donghi007]

@ww1g11 Thank you for repairing this bug :)
I replaced the old one, now it works fine!

Thanks again :) !