Zeeman digram of Ising spins at certain angle

[Eufemio]

Dear Stefan,

I have a question regarding levels plot in easyspin and I was wondering if you could give me some help.

You see, I want to simulated two ising spins 3/2 at 60º of each other with a ferromagnetic exchange interaction and ZFS, and calculate the Zeeman diagram with the field parallel and perpendicular the mean ferromagnetic exchange. To do this used euler angles rotating both spins 30º degrees off the z-componet. (see parameters below)

D = [-100]; J = [+1]; g = [0 0 20];
Sys.S = [3/2;3/2];
Sys.g = [g; g];
Sys.D = [D; D]*29980;
Sys.ee = [J]*-29980;
Sys.gFrame = [0 30 0; 0 -30 0]*pi/180;

ETranverse = levels(Sys,[0,pi/2],simField);
EParallel = levels(Sys,[0,0],simField);

With this values I get a good Zeeman diagram.

Next, just for the sake of curiosity I tried to do the same but fixing the first spin at 0º and rotating the second spin 60º. Now the parallel and traverse will be situated at 30º and 120º off the Z-projection respectively, so I used the script below to get the plot.

D = [-100]; J = [+1]; g = [0 0 20];
Sys.S = [3/2;3/2];
Sys.g = [g; g];
Sys.D = [D; D]*29980;
Sys.ee = [J]*-29980;
Sys.gFrame = [0 0 0; 0 60 0]*pi/180;
FieldRange = [0 500];

ETranverse = levels(Sys,[0,120*pi/180], FieldRange);
EParallel = levels(Sys,[0,30*pi/180], FieldRange);

I was expecting the same result for both cases, however I have two different Zeeman plots. Actually using the second approach is not the expected level diagram.

Why are they different? Could you please tell me what I'm doing wrong?

Thanks for your help.

Eufemio

[Stefan Stoll]

You have to rotate the tensor frames of all anisotropic tensors. You only rotated the g frames, but forgot to rotate the D frames.

Here is an example that should work:

Code: Select all

Sys.gFrame = [0 -30 0; 0 30 0]*pi/180;
Sys.DFrame = [0 0 0; 0 0 0];
E1 = levels(Sys,[0,90]*pi/180,FieldRange);

Sys.gFrame = [0 0 0; 0 60 0]*pi/180;
Sys.DFrame = [0 30 0; 0 30 0]*pi/180;
E2 = levels(Sys,[0,120*pi/180], FieldRange);

[Eufemio]

Indeed I was not rotating D, thank you very much Stefan...!
Cheers,
Eufemio

[Stefan Stoll]

You're welcome!