[Wien] Non-collinear magnetism in WIEN2k? Total magnetic moment, spin moment and orbital moment...

[Pavel Novak]

Dear Pablo,

if M is not along the symmetry axis, the spin orbit coupling will cant the
spin out of the direction prescribed for magnetization in case.inso. Also
orbital moment will deviate from it. Both spin and orbital moment are
calculated in LAPWDM, which allows determination of all components of
these vectors. Note that there is some inconsistency: M direction is
prescribed in case.inso, but after finishing the calculation, you'll find
magnetization in different direction. The reason is that you keep along
the selected direction the exchange field, but the total field is sum of
the exchange field and 'field' from spin-orbit coupling s<l>.

As to your second question: in LAPWDM you calculate the spin moment from
selected electrons only (usually d or f), while moment in the sphere is
the sum from all electrons: you can check it by running LAPWDM for all s,
p, d and f states.

Pavel


 On Mon, 21 Apr 2008, Pablo de la
Mora wrote:

> When one adds spin-orbit coupling for a magnetic system one has to
> define a magnetization direction in '<case>.inso':
>    0.  1.  0.                 direction of magnetization (lattice vectors)
>
> The results of the calculation come out in the <case>.scf file. There
> are three different results, the total magnetic moment, the spin moment
> and the orbital moment:
> MAGNETIC MOMENT IN SPHERE   1    =    1.24926
> SPIN MOMENT:  -0.03321   1.15380   0.00000 PROJECTION ON M  1.15380
> ORBITAL MOMENT:  0.14357 -1.02102  0.00000 PROJECTION ON M -1.02102
>
> There are two kind of questions that I have:
> 1) Why are these spin and orbital moments given in vector form?
>     Does this imply a kind of non-colinear magnetism?
>     If this is the case I would presume that it is valid for small
> deviations from the magnetization direction, in this case the deviation
> is of 8 degrees for the orbital moment and 1.5 degrees for the spin
> moment. For these relatively small angles, are these values correct?
>
> 2) In the <case>.scf file :MMI001 gives the 'MAGNETIC MOMENT IN SPHERE',
> but with spin-orbit coupling the 'SPIN MOMENT' and the 'ORBITAL MOMENT'
> appear. So what is the total magnetic moment in this case?
>
> Adding spin and orbital gives:
> 0.11036  0.13278  0.00000 PROJECTION ON M 0.13278
>
> as it can be seen it is much smaller than the MAGNETIC MOMENT IN SPHERE.
>
> I have observed that magnetic moment in sphere and the spin moment are
> quite symmilar but not equal, Do they have, in principle, the same
> meanning? Which is the correct one?
>
>     Yours
>
>                    Pablo de la Mora
>
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