coercivity of CoFeB

[sira...@gmail.com]

i am trying to reproduce the coercivety in the below mentioned article. but i am unable to make it 

. as i tried alot of test to produce suck like loop but not success.

https://www.nature.com/articles/s41598-017-16911-3

here is my input and material file.

#------------------------------------------
create:crystal-structure = bcc
create:periodic-boundaries-x
create:periodic-boundaries-y
#------------------------------------------
# System Dimensions:
#------------------------------------------
dimensions:unit-cell-size-x = 2.86 !A

dimensions:system-size-x = 10 !nm
dimensions:system-size-y = 10 !nm
dimensions:system-size-z = 1 !nm


#------------------------------------------
# Material Files:
#------------------------------------------
material:file = vse2.mat
#------------------------------------------
# Simulation attributes:
#------------------------------------------
sim:temperature = 5
sim:maximum-applied-field-strength= 1.5 !T
sim:applied-field-strength-increment=0.05 !T
sim:applied-field-angle-phi = 0.1
sim:equilibration-time-steps=100000
sim:loop-time-steps=100000
sim:time-steps-increment=1
sim:time-step=1e-16
sim:applied-field-unit-vector= 0, 0, 1
#------------------------------------------
# Program and integrator details
#------------------------------------------
sim:program = hysteresis-loop
sim:integrator = llg-heun
#------------------------------------------
# data output
#------------------------------------------
output:real-time
output:applied-field-strength
output:magnetisation


#---------------------------------------------------
# Number of Materials
#---------------------------------------------------
material:num-materials=2
#---------------------------------------------------
# Material 2 (CoFeB bulk layer)
#---------------------------------------------------
material[1]:material-name=FM
material[1]:damping-constant= 1.0
material[1]:exchange-matrix[1]=7.735e-21
material[1]:exchange-matrix[2]=7.735e-21
material[1]:atomic-spin-moment=1.6 !muB
material[1]:uniaxial-anisotropy-constant= 0
material[1]:material-element=Fe
material[1]:minimum-height=0.0
material[1]:maximum-height=0.8
material[1]:initial-spin-direction=0,0,1

#---------------------------------------------------
# Material 2 (CoFeB interface layer)
#---------------------------------------------------
material[2]:material-name=CoFeB
material[2]:damping-constant= 1.0
material[2]:exchange-matrix[1]=7.735e-21
material[2]:exchange-matrix[2]=1.547e-20
material[2]:atomic-spin-moment=1.6 !muB
material[2]:uniaxial-anisotropy-constant=1.35e-22
material[2]:material-element=Ag
material[2]:minimum-height=0.8
material[2]:maximum-height=1.0
material[2]:initial-spin-direction=0,0,1
#---------------------------------------------------

plz someone look out my files is it ok.

i just get 1 magnetization and its not converging i need your help

[gabo...@gmail.com]

For testing purposes only, I reduced the time-steps in your input file from 100000 to 25000.  I also increased the maximum-applied-field-strength.

As seen in the attached image file (CoFeB_loop.png),  I see after running the VAMPIRE 6.0.0 simulation a hysteresis loop with a corecivity of about 4 T.  Thus, your maximum-applied-field-strength of 1.5 T is too small as that value needs to be larger than the corecvity.

Shape anisotropy might also have a significant affect on the simulation result.  I didn't try visualizing the simulation result [1].  However, looking at your input file, it looks likely to be for a 10 nm square.  Whereas, it looks like there is a 50 nm cylinder shape in Figure 1 of the Nature article [2] that you referenced.

The VAMPIRE website has a tutorial page with an example of a cylinder [3].  Based on that tutorial, it looks like your input file would be missing lines for having cylinder.

[1] https://vampire.york.ac.uk/resources/workshop2017_day4B.pdf

[2] https://doi.org/10.1038/s41598-017-16911-3

[3] https://vampire.york.ac.uk/tutorials/atomistic-system-generation/

Hopefully that helps and kind regards,

Gavin

VAMPIRE user