[Wien] magnetic anisotropy and zero-field splitting

[novakp at fzu.cz]

Dear Bin,

for localized, strongly correlated electrons, the problem with all
single-electron-like calculations, including WIEN2k, is that you'll not
get the multiplets. DMFT can do it, but it is still too complicated and
also parameter dependent. In this situation what one can try is to use
WIEN2k
to calculate parameters of the effective Hamiltonian, which includes full
electron-electron and magnetic interactions. To this end I use strongly
modified Swedish program 'lanthanide', but there are other similar
programs available

Regards
Pavel
> Dear Prof. Novak,
>
> Thank you for your reply!
>
> As you mentioned, these interactions can be projected to the ground spin
> multiplet, deducing an effective spin Hamiltonian.
>
> Usually, the MAE can be calculated by the difference in total energy
> between different magnetization directions. I have no idea how to
> correlate these energy difference to the spin multiplet. For assuming
> c-axis is the easy axis and the S is larger than 1/2. When the
> magnetization direction is along the c-axis, the system is under the
> ground state, whether if I can say this corresponds to the ground state in
> zero-field splitting. And when the magnetization direction is along the
> hard-axis, whether if I can say the system is under the excited states in
> zero-field splitting. My question is how to map the states with different
> magnetization directions to the spin multiplet.
>
> Best regards,
>
> Bin
>
>
>
> Bin Shao
> Postdoc
> Department of Physics, Tsinghua University
> Beijing 100084, P. R. China
> Email: binshao1118 at gmail.com
>
> From: novakp
> Date: 2014-10-04 16:39
> To: A Mailing list for WIEN2k users
> Subject: Re: [Wien] magnetic anisotropy and zero-field splitting
> Dear Bin Shao,
>
> single ion anisotropy results from coupling of the spin of atom to the
> magnetization by exchange interaction and to orbital moment of the atom
> by
> spin-orbit interaction. Orbital moment feels the crystal lattice due to
> the crystal field. One can project above interactions on the ground spin
> multiplet - the results is an effective spin Hamiltonian, which besides
> the exchange field contains the zero field splitting characterized by
> parameters D, a, etc. From EPR measurement on the isostructural
> nonmagnetic compound one can get an approximation for the D parameter. In
> WIEN the effective Hamiltonian parameters for rare earths may be
> calculated using the program CFP, which I recently put in 'Unsupported
> software goodies' on
> the WIEN2k web site. In principle the program might be also used for the
> 3d compounds, the problem is that in the first step calculation with 3d
> states in the core is required, and because of the 3d-states more
> delocalized compared to the 4f, the charge may leak out of the atomic
> sphere.
>
> Best regards
> Pavel
>
>
>> Dear all,
>>
>> I am puzzled by the conception of single ion anisotropy and zero-field
>> splitting.  In wien2k, we can calculate magnetic anisotropy energy
>> (MAE)
>> of single ion by evolving spin-orbit coupling. However, in most
>> experiments, another conception, zero-field splitting (ZFS),
>> parametering
>> by the D term, usually will be measured by EPR or spin polarized STM.
>> ZFS
>> is the removal spin microstate degeneracy for systems with S > 1/2 in
>> the
>> absence of an applied field and also causes magnetic anisotropy. I am
>> wondering what is the relationship between the MAE and ZFS or how to
>> calculate the D-term in wien2K?
>>
>> Any comments and suggestions will be appreciated. Thank you in advance!
>>
>> Best regards,
>>
>>
>>
>>
>> Bin Shao
>> Postdoc
>> Department of Physics, Tsinghua University
>> Beijing 100084, P. R. China
>> Email: binshao1118 at gmail.com
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