[Wien] Treating 4f states as core

[Ali Baghizhadeh]

Thank you very much for your comments Prof. Laurence. Your paper is one of my references to do my set of calculations, and interprate my EELS data later on. Basically h-REFeO3 (RE: Lu, Yb, Sc ..) is AFM basal plane with non-collinear spins of Fe3+. Magnetism of Yb should contribute on c-axis weak FM component. and I wish to know if this is ground state of the system or not?
best regards
Ali
________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Laurence Marks <laurence.marks at gmail.com>
Sent: Thursday, April 9, 2020 3:47 AM
To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
Subject: Re: [Wien] Treating 4f states as core

Treating the Ln atoms as core ignores the crystal field splitting. In my opinion it is an approximation used in to get the calculation to converge, except for La & Gd I cannot justify it.

The Hubbard +U puts the 4f very low in energy, in effect "shoves them out of the way". Based upon our analysis in DOI: 10.1103/PhysRevMaterials.2.025001 it is not right in many cases, rather a pragmatic approximation to get converged results which are insulators.

Based upon the paper on YbFeO3, which is experiment, the Yb are "up" and the Fe are "down" if I have read it right. If you replace Yb with Sc, since Sc3+ is non-magnetic I would expect the Fe spins to remain the same and the system will be ferromagnetic.

There are probably many papers where people have done calculations on systems such as this and obtained physically unreasonable or incorrect results.

On Thu, Apr 9, 2020 at 10:01 AM Ali Baghizhadeh <ali.baghizhadeh at ua.pt<mailto:ali.baghizhadeh at ua.pt>> wrote:
Dear Prof. Laurence
Thank you. In the mentioned paper, they treated Yb 4f electrons  as valance while some for HoMnO3 or DyFeO3, treated 4f electrons as core. I do not know what is the best approach?
For most h-LuFeO3 family there is experimentally a weak FM, and there are some ideas on its origin, while the lattice is AFM. For YbFeO3, I did similar calculation like the paper you are quoting, and it is AFM. When I do doping with Sc (4 Sc and 2 Yb ions), it always switches to FM.
Bets regards.
Ali

________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at<mailto:wien-bounces at zeus.theochem.tuwien.ac.at>> on behalf of Laurence Marks <laurence.marks at gmail.com<mailto:laurence.marks at gmail.com>>
Sent: Thursday, April 9, 2020 1:58 AM
To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at<mailto:wien at zeus.theochem.tuwien.ac.at>>
Subject: Re: [Wien] Treating 4f states as core

Let me turn this thread around a bit, as it seems to be endless. There are several possible reasons you are not getting an AFM solution, the two main ones being:
a) You are doing the calculation wrong.
b) It is not AFM.

What is the evidence that it should be AFM? Your opinion, or uncontroversial experimental evidence?

Based on DOI: 0.1103/PhysRevB.95.224428 it is not AFM!

_____
Professor Laurence Marks
"Research is to see what everybody else has seen, and to think what nobody else has thought", Albert Szent-Gyorgi
www.numis.northwestern.edu<http://www.numis.northwestern.edu>

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--
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu<http://www.numis.northwestern.edu/>
Corrosion in 4D: www.numis.northwestern.edu/MURI<http://www.numis.northwestern.edu/MURI>
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what nobody else has thought"
Albert Szent-Gyorgi
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