[Pw_forum] Doubt in Curie temperature value

[German Samolyuk]

Hi,

The difference between FM and AFM energies gives 2J_0, I think. It's easy to
check for nearest neighbors interactions only.
In this case for Fe your result is quite reasonable. Fe is itinerant
ferromagnetic but with localized magnetic moments and
Heisenberg model works quite good. You can look for exchange parameters
calculated through linear response expression.
There is a lot of publication on this topic. For Fe exchange potentials
looks like: large first neighbors interactions and the oscillations.
So the rest of neighbors almost compensate each other.
Ni is a different story. I do not know if anybody can calculate Curie
temperature in Ni correctly. It's significantly smaller and if I'm right and

delta E = 2 J_0 result for Ni is even smaller in your calculations in
agreement with other results.

Sincerely,

German Samolyuk,
ORNL



On Tue, Mar 22, 2011 at 12:57 AM, Padmaja Patnaik <
padmaja_patnaik at yahoo.co.uk> wrote:

> Hi
>
> I am calculating the Curie Temperature for Iron. The experimental value for
> this is  1043 K. I am getting the value as 2398.97 K. I am using the
> following way to calculate.
> Find out the ferromagnetic and anti-ferromagnetic energy of Fe. The
> difference between these two gives the value of J_0. Then,
> T_c = [2/3] [J_0/K_B]
>
> Please suggest me what is wrong? Why am I getting such a high value. On the
> other hand I am getting very low value for Ni, whose experimental Curie
> temperature is 627K and I am getting 315K.
> Thanking you in advance,
> regards
> Padmaja Patnaik
> Research Scholar
> Dept of Physics
> IIT Bombay
> Mumbai, India
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20110323/19f5ba6e/attachment.html>