Dear collegues,
based on our measurements of MOKE spectra, we think that the
magnetooptic off-diagonal permittivity in the file case.jointup has
opposite sign, as compared to the experiment. For example, in the case
of [001] magnetization, column Re_eps_xy in the file case.jointup has
opposite sign, as compared to the experimental spectra.
Namely, we made careful sign tests on bcc Fe. Then, according to our
experiment, Re_eps_xy should be negative for energy about 2 eV, but the
permittivity calculated by wien2k, Re_eps_xy, has positive sign.
This statement is further supported for example by spectra in article
Oppeneer et al, PRB45 10924 (1992),
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.45.10924
figure 3b, where after conversion of the off-diagonal conductivity to
the permitivity (ep=i*sigma/(omega*ep0)) it provides negative real part
of the off-diagonal permittivity at about 2eV as well.
Furthermore, we have written our own integration over BZ of the
transition matrix elements, and transition matrix elements (files
case.symmatup, case.mommat2up) seems to us to be sign-correct.
We think, wrong sign in Re_eps_xy simply appears in conversion from
conductivity (calculated by Kubo formula, OPT1.f) to the outgoing
permittivity.
We think this step appears on lines 965 and 985 of file joint.f, w2k
version 18.2:
VV=EPSF*DENSTY(IB,J,icol)/ENG2(j)
where division by the energy makes basically conversion from the
conductivity to the permittivity.
However, as the conversion itself handles complex numbers:
eps = i/omega * sig
the conversion between real and imaginary parts have opposite signs
eps_Im = sigma_Re/omega (this is correct in code)
eps_Re= - sigma_Im/omega (this is the expression for the off-diagonal
permittivity induced by magnetization, and in this case, we think minus
sign is missing in the code, namely for Re_eps_xy, Re_eps_xz and
Re_eps_yz. )
Probably, those arguments will apply also for X-ray off-diagonal spectra
elements (line 906 in joint.f).
Hoping my comment will be useful to improve w2k code.
With my best regards
Jaroslav Hamrle & Ondrej Stejskal
--
------------------------------------------------------------------
Mgr. Jaroslav Hamrle, Ph.D.
Institute of Physics, room F232
Faculty of Mathematics and Physics
Charles University
Ke Karlovu 5
121 16 Prague
Czech Republic
tel: +420-95155 1340
email: ham...@karlov.mff.cuni.cz
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