Mp-474 ErFe2 and mp-1071340 ErFe2 Magnetic moment

#1

Dear Expert

I am trying to seek the Final Magnetic Moment calculation of ErFe2 found
1- mp-474 ErFe2 -0.003 μB Magnetic Ordering Non-magnetic
2- mp-1071340 ErFe2 Final Magnetic Moment 6.398 μB
Magnetic Ordering Ferri

I hope I can get explanation of the difference between the two magnetic and ordering results

Thank you

#2

Hi sherif_Yehia,

Generally the Non-magnetic label applies to any materials or calculations which have resulted in zero or very low magnetic moments. Ferrimagnetism results in partially inverted magnetic moments. The second assignment might change in the coming weeks, as we’re revising some of the magnetic phase assignments in our ongoing builder refactor, but you can also get the final magnetic moments output by the VASP calculation as those attached to the structure, e. g.:

mpr = MPRester()
structure = mpr.get_structure_by_material_id("mp-1071340")
print(structure.site_properties['magmoms'])
>>> [-0.615, -0.615, 1.952, 2.059, 2.04, 1.76]
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#3

Hi Joseph_Montoya
Thanks for your clear reply regarding ErFe2 mp-1071340 . Yes Ferrimagnetism as you mention in partially inverted magnetic moments in the VASP calculations. For this system we have found a reference to a possible non-collinear magnetic structure in ErFe2 compound
Magnetic and magnetocaloric properties of Er(Co1_xFex)2 intermetallic
Compounds I. Chaaba et al
http://dx.doi.org/10.1016/j.jmmm.2017.05.033
http://refhub.elsevier.com/S0304-8853(17)30742-4/h0125

The magnetic moment per formula unit is about 5.7 Bohr magnetons as reported by
Molecular-field theory analysis of RFe, intermetallic compounds
Y.J. Tang, et. a.l
Journal of Magnetism and Magnetic Materials 127 (1993) 378-382
My question is: is there an option in the VASP code to allow for handling such magnetic structure?
Thank you for all the kind help

#4

I believe it is possible to perform non-collinear magnetic calculations in VASP (see the user manual’s entry on LNONCOLLINEAR, but I’ve heard from my colleagues it can be a bit painful to both implement and interpret the results. @mkhorton is our resident magnetism expert, so he can likely comment more intelligently on this.

1 Like
#5

Yes, I concur with @Joseph_Montoya on this.

A non-collinear calculation is definitely possible for the ErFe2, would be more difficult for the Er(Co_{1-x}Fe_{x})_{2} case. Erbium generally is a tricky element to get right though.

Non-collinear calculations are currently not supported by Materials Project, so you’d have to try it yourself. The manual that @Joseph_Montoya linked is a good reference.

#6

Hi Joseph & Mkhorton

Thanks v. much for the guidance regarding ErFe2 and sorry for my late reply

I agree it is tricky element and VASP is very restricted software unfortunately we have it :disappointed: but not for my group . I wish there is any direction using python or wien2k I have it
Not trusted for Non-collinear calculations
Thanks again for all the kind help

#7

Dear Expert
I asked this question before regarding ErFe2 mp-474
the calculated magnetic moment for the FiM solution was 6.398 μB
now it is Final Magnetic Moment is 3.199 μB on the site
Magnetic Ordering FiM
Can I get some help to see the difference
Thanks in advance for your time and effort

#8

Hi @sherif_Yehia,

The reported final magnetic moment is per the displayed unit cell: it is not normalized per volume or formula unit currently. Until we change this data to show magnetic moment per formula unit, we always recommend you inspect the structure manually. It might be that this moment is coming from a smaller unit cell; I will verify this.

However, for the specific case of for mp-474, we see that:

Full Formula (Er2 Fe4)
Reduced Formula: ErFe2
abc   :   5.100696   5.100696   5.100695
angles:  60.063386  60.063386  60.063387
Sites (6)
  #  SP            a          b          c    magmom
---  ----  ---------  ---------  ---------  --------
  0  Er     0.625239   0.625239   0.625239    -0.615
  1  Er     0.374761   0.374761   0.374761    -0.615
  2  Fe    -0         -0         -0            1.952
  3  Fe    -0         -0          0.5          2.059
  4  Fe    -0          0.5       -0            2.04
  5  Fe     0.5       -0         -0            1.76

Here, the sum is 6.58µB, which is similar to that reported previously.

Best,

Matt

#9

Hi mkhorton
Thank you, v., much for the clear reply, regarding ErFe2 -mp-474. I hope you can tell the space group used in calculating the magnetic moment of the ErFe2 per unit cell. I used the .cif file symmetrized from your site with H-M Fd-3m (227) space group unfortunately the magnetic moment was far from your calculation.

Thanks for your effort and time

Best regards
Sherif