[Wien] Antiferromagnetic Calculation With Orbital Potentials

[David Tompsett]

Dear All,
             I am studying the magnetic ground state of a metallic 
system. The magnetic atoms are Yb, and I am localizing the 4f moment 
using an orbital potential, as well as applying spin-orbit coupling.

I have a question about the behaviour of the spin moments depending on 
my input to case.inst
Firstly, I set the starting spins such that the 5d electron and 4f hole 
have a net spin and are flipped between the two Yb atoms:
Yb
Xe 4 
4, 3,3.0  N
4, 3,3.0  N
4,-4,4.0  N
4,-4,3.0  N
5, 2,1.0  N
5, 2,0.0  N
6,-1,1.0  N
6,-1,1.0  N

Yb2
Xe 4 
4, 3,3.0  N
4, 3,3.0  N
4,-4,3.0  N
4,-4,4.0  N
5, 2,0.0  N
5, 2,1.0  N
6,-1,1.0  N
6,-1,1.0  N
In this case the moments between the two Yb atoms go towards spin 
moments of +2u and -1u during the convergence. Not an antiferromagnetic 
solution.

Second, I set the 6s spin to 0.5 up and 0.5 down( ie. not net spin) in 
case.inst:
Yb
Xe 4 
4, 3,3.0  N
4, 3,3.0  N
4,-4,4.0  N
4,-4,3.0  N
5, 2,0.5  N
5, 2,0.5  N
6,-1,1.0  N
6,-1,1.0  N

Yb2
Xe 4 
4, 3,3.0  N
4, 3,3.0  N
4,-4,3.0  N
4,-4,4.0  N
5, 2,0.5  N
5, 2,0.5  N
6,-1,1.0  N
6,-1,1.0  N
Then, a stable antiferromagnetic solution was found.

Questions:
1) Does the different behaviour occur because I am only applying my 
orbital potential to the 4f states and not 5d?

2) Is there some other physics to explain this? Is there something that 
I can check to diagnose the behaviour in the first case?

Thanks,
David.

-- 
David A. Tompsett
Quantum Matter Group
Cavendish Laboratory
J. J. Thomson Avenue
Cambridge CB3 0HE
U.K.
Tel: +44 7907 566351 (mobile)
Fax: +44 1223 768140
http://www-qm.phy.cam.ac.uk/