How to calculate the Hysteresis cycle of Cobalt

The Vampire code calculate the magnetic properties at the nano scale using the Monte Carlo method.

We will calculate the hysterisis cycle of the hexagonal cobalt. 

We need 2 input files

Input

#------------------------------------------
# Sample vampire input file to perform
# a Hysteresis loop simulation for Co.
# crystal-structure and unit-cell-size from Table 2
# https://doi.org/10.1088%2F0953-8984%2F26%2F10%2F103202
#------------------------------------------
#------------------------------------------
# Creation attributes:
#------------------------------------------
create:crystal-structure=hcp

#------------------------------------------
# System Dimensions:
#------------------------------------------
dimensions:unit-cell-size = 2.507 !A
dimensions:system-size-x = 2 !nm
dimensions:system-size-y = 2 !nm
dimensions:system-size-z = 3 !nm

#------------------------------------------
# Material Files:
#------------------------------------------
material:file=Co.mat

#------------------------------------------
# Simulation attributes:
#------------------------------------------

sim:loop-time-steps=1500
sim:time-step=1.0e-15
sim:temperature=0
sim:maximum-applied-field-strength=3.5 !T
sim:applied-field-strength-increment=0.015 !T
sim:applied-field-unit-vector=0,0.001,0.999


#------------------------------------------
# Program and integrator details
#------------------------------------------
sim:program=hysteresis-loop
sim:integrator=llg-heun

#------------------------------------------
# data output
#------------------------------------------
output:real-time
output:applied-field-strength
output:material-magnetisation

 

Co.mat

#===================================================
# Sample vampire material file for Cobalt
#===================================================

#---------------------------------------------------
# Number of Materials
#---------------------------------------------------
material:num-materials=1
#---------------------------------------------------
# Material 1 hcp Cobalt
# exchange-matrix, atomic-spin-moment,
# and uniaxial-anisotropy-constant from Table 2
# https://doi.org/10.1088%2F0953-8984%2F26%2F10%2F103202
#---------------------------------------------------
material[1]:material-name=Co
material[1]:damping-constant=1
material[1]:exchange-matrix[1]=6.064e-21
material[1]:atomic-spin-moment=0.606 !muB
material[1]:uniaxial-anisotropy-constant=6.69e-24
material[1]:material-element=Co

 

Calculation

/vampire-tutorials/Hysteresis/Co> vampire-serial

 

To plot the results we need the following gnuplot script 

 Co.gnu

set xlabel "Applied field (T)"
set ylabel "m_z"
p "output" u 2:5 w p

 

/vampire-tutorials/Hysterisis/Co> gnuplot --persist Co.gnu

 

We get the following plot