Hysterisis loop

[Shabeer ali pc]

Hi all.

I am new to vampire. I have a doubt mentioned below

I have attached an image of the drawn Hysteresis loop using below input and mat file. Correct me, but what happened to my result like this?

kindly support for my doubts.

Thanks & Regards.

[gabo...@gmail.com]

It looks like you defined your simulation case with an easy axis in the x-direction.

Your "Hysterises loop.png" shows you plotting mx (on the y-axis).

From that, I'm assuming you are wanting to look at the easy axis loop for mx when there is an applied field in the x-direction.

One potential issue I see in your input file is that you have the applied field in the z-direction:

sim:applied-field-unit-vector= 0, 0, 1

In your input file, I also see you have "sim:temperature=0".  Based on what is described at [1], it is suggested to break the symmetry for the applied field a little bit so that the magnetic moments will get a torque.  An analogy sometimes used to introduce this concept is it being similar to a ball that perfectly sits on top of a hill were it won't roll:

To have the applied field in the x-direction, you could set:

sim:applied-field-unit-vector= 0.999, 0.001, 0

Another potential issue could be that your applied field 20 T is not enough to overcome the coercivity (Hc) for the simulation case you have defined in the input file and Fe2NiTi.mat file.  You could give 150 T a try:

sim:maximum-applied-field-strength=150.0

I changed some other values, as given in the attached input file, so that a simulation would complete faster but with less accuracy.  However, you will probably not want to change them for obtaining more accurate results.  The simulation with the modified input file was ran as shown below giving a plot where Hc of the loop occurred between about 100 and 150 T.  Though, Hc might change when you perform convergence testing with the time-step parameters.

username@computername:~/Fe2NiTi$ ls
Fe2NiTi.mat  input  mxVsHplot.gnu
username@computername:~/Fe2NiTi$ ~/vampire/vampire-serial
                                                _          
                                               (_)        
                    __   ____ _ _ __ ___  _ __  _ _ __ ___
                    \ \ / / _` | '_ ` _ \| '_ \| | '__/ _ \
                     \ V / (_| | | | | | | |_) | | | |  __/
                      \_/ \__,_|_| |_| |_| .__/|_|_|  \___|
                                         | |              
                                         |_|              

                      Version 6.0.0 May 26 2024 20:12:55

             Git commit: 4c9651daecc86c3e6b6df0c8055fcd9e89fd900c
...
Simulation ended gracefully.
username@computername:~/Fe2NiTi$ gnuplot --persist mxVsHplot.gnu

[1] https://groups.google.com/g/vampire-users/c/faPqxkUKOuw/m/t2kIrgIQBv8J

Kind Regards,

Gavin

VAMPIRE user