How to calculate the Curie temperature and magnetic phase transition of Nickel

 We take the example of Nickel which has a Curie temperature value of 640 K. We will calculate the magnetic phase transition and deduce the Curie temperature value from the plot.

input

#------------------------------------------ 
# Creation attributes: 
#------------------------------------------ 
create:crystal-structure=fcc 
create:periodic-boundaries-x 
create:periodic-boundaries-y 
create:periodic-boundaries-z 
#------------------------------------------ 
# System Dimensions: 
#------------------------------------------ 
dimensions:unit-cell-size = 3.524 !A 
dimensions:system-size-x = 4.0 !nm 
dimensions:system-size-y = 4.0 !nm 
dimensions:system-size-z = 4.0 !nm 
#------------------------------------------ 
# Material Files: 
#------------------------------------------ 
material:file=Ni.mat 
#------------------------------------------ 
# Simulation attributes: 
#------------------------------------------ 
sim:temperature=300 
sim:minimum-temperature=0 
sim:maximum-temperature=800 
sim:temperature-increment=25 
sim:time-steps-increment=1 
sim:equilibration-time-steps=1000 
sim:loop-time-steps=1000 
#------------------------------------------ 
# Program and integrator details 
#------------------------------------------ 
sim:program=curie-temperature
sim:integrator=monte-carlo
#------------------------------------------ 
# Data output 
#------------------------------------------ 
output:real-time
output:temperature
output:magnetisation 
output:magnetisation-length 
output:mean-magnetisation-length 

Ni.mat

#--------------------------------------------------- 
# Number of Materials 
#--------------------------------------------------- 
material:num-materials=1 
#--------------------------------------------------- 
# Material 1 Nickel Generic 
#--------------------------------------------------- 
material[1]:material-name=Ni 
material[1]:damping-constant=0.01 
material[1]:exchange-matrix[1]=2.757e-21 
material[1]:atomic-spin-moment=0.606 !muB 
material[1]:uniaxial-anisotropy-constant=0.0 
material[1]:material-element=Ni

Calculation

/vampire-tutorials/Ni> vampire-serial

/vampire-tutorials/Ni> gnuplot

gnuplot> p "output" u 2:8 w l 

We get the following picture

For detailed information check the following video: