[Wien] magnetic anisotropy and zero-field splitting

[binshao1118 at gmail.com]

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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