Dear Alex,

You addressed your email to "experts on magnetic refinement" so I
apologise if I am the only person to reply for I am a lowly PhD student.

I am afraid I am not going to answer your questions directly but instead
point you to the program that I use for magnetic refinements. Its free
software available on CCP14 called SARAh. It allows you to input your
magnetic atom sites, space group and k-vector then has the ability to
modify your fullprof pcr file depending on how you wish to do the
refinement.

The process is a little involved, as it uses representational theory to
reduce your problem to symmetry allowed structures, rather than freely
refining all variables, but it has step by step instructions and I think
there are even some online help videos for using it now.

Available from:
www.CCP14.ac.uk  or
www.chem.ucl.ac.uk/people/wills/index.html

Best regards and good luck
Ross Colman


> Dear experts on magnetic refinement,
>
> We recently got some nice data on GEM, ISIS and I was able to get a decent
> structural fit using GSAS and FullProf.
>
> Now I would like to refine the magnetic structure but this is my first
> time
> so I struggle to give FullProf what it wants.
>
> Since I'm a novice treating the magnetic data I'd have some general
> questions about the input (which I attached below). The general structure
> of
> the pcr file seems to be OK, because it is read by FP but unfortunately in
> the current form leads to a singular matrix. I'm sure I've done something
> wrong with the input parameters.
>
> Here is a quick outline of what I want to achieve:
> There are two magnetic ions in the structure. Mn and Co, but Co has a very
> small moment (we know that from neutron diffraction from the 80's). The
> moments seem to order in two incommensurate spiral structures (one for Mn
> and one for Co) with the k-vector along c-axis. I thought it is best to
> include a separate purely magnetic phase in FP. Would you agree and if yes
> can I still do a multi-bank refinenment?
>
> Here is the snippet from the pcr file which was inspired by Ho2Cu2O5, an
> example from the FP webpage (questions below):
> ----------------------------------------------------------------------------------------------------------------------------------------------
> CoMnSi(magnetic
> reflection)
>
> !
> !Nat Dis Mom Jbt  Isy Str Furth        ATZ     Nvk More
>    2   0   0 -1    -1  0   0          0.0000   2   1
> !Jvi Jdi Hel Sol Mom Ter
>  3   0   0   0   0   0
> !Contributions (0/1) of this phase to the  6 patterns (FOR simplicity I
> deleted all but the first pattern to get started)
>  1
> !Irf Npr Jtyp  Nsp_Ref Ph_Shift for Pattern#  1
>   -1  13   -1      0      0
> ! Pr1    Pr2    Pr3   Brind.   Rmua   Rmub   Rmuc     for Pattern#  1
>   0.000  0.000  1.000  1.000  0.000  0.000  0.000
> P -1                  <--Space group symbol
> !Nsym Cen Laue MagMat
>    4       1         3        1
> !
> SYMM  x,y,z
> MSYM  u,v,w,0.0
> SYMM -x,-y,z+1/2
> MSYM  u, v,-w,0.0
> SYMM  x+1/2,-y+1/2,z
> MSYM -u,v,-w,0.0
> SYMM -x+1/2,y+1/2,z+1/2
> MSYM  u,-v,-w,0.0
> !
> !Atom   Typ   Mag Vek    X        Y        Z     Biso       Occ      Rm
> Rphi  Rtheta
> !       Im   Iphi   Itheta        beta11   beta22   beta33   MagPh
> Co1     MCO2     1   1   0.15609  0.25000  0.05324  0.00000   1.00000
> 0.3    23.0
> 45.0
>
>                         220.00     0.00   230.00   280.00      0.00   0.0
> 0.0       0.0
>       0.00000  0.00000  0.00000  0.00000  0.00000   0.00000
>          0.00     0.00     0.00     0.00     0.00      0.00
> Mn1     MMN2     1   2   0.02093  0.25000  0.68070  0.00000   1.00000
> 3.1     178.0
> 13.0
>
>                          0.00     0.00     0.00     0.00      0.00
> 0.0      0.0      0.0
>       0.00000  0.00000  0.00000  0.00000  0.00000   0.00000
>          0.00     0.00     0.00     0.00     0.00      0.00
> !-------> Profile Parameters for Pattern #  1
> !  Scale       Extinc      Bov     Str1     Str2     Str3    Strain-Model
>   4.8798       0.0000   0.0000   0.0000   0.0000   0.0000       0
>     1.00000     0.00     0.00     0.00     0.00     0.00
> !     Sig-2      Sig-1      Sig-0        Xt         Yt         Z1
> Z0      Size-Model
> !     0.000    186.666      0.000 <- Instr. par. + shifts. Only shifts are
> refined
>       0.000     33.363      0.000      0.000      0.000      0.000
> 0.000   0
>      350.00      31.00       0.00       0.00       0.00       0.00
> 0.00
> !    Gam-2     Gam-1     Gam-0     LStr       LSiz
> !    0.000     0.000     0.000 <- Instr. par. + shifts. Only shifts are
> refined
>      0.000     0.000     0.000     0.000     0.000
>       0.00      0.00      0.00      0.00      0.00
> !     a          b         c        alpha      beta       gamma      #Cell
> Info
>    5.866537   3.692333   6.856417  90.000000  90.000000
> 90.000000
>
>    0.00000    0.00000    0.00000    0.00000    0.00000    0.00000
> !      Pref1      Pref2        alph0       beta0       alph1       Kappa
> !  Instr. par. + shifts:    1.597107   24.016417    1.496805   46.025921
> <-
> Only shifts are refined
>     1.000000    0.000000    0.000000   -3.937651    0.000000    0.000000
>         0.00        0.00        0.00       40.00        0.00        0.00
> !Absorption correction parameters
>    0.00000    0.00   0.00000    0.00            ABS: ABSCOR1  ABSCOR2
> !Propagation vector 1
> 0.00000   0.00000   0.2300000
> 0.00      0.000     1.000
> !Propagation vector 2
> 0.00000   0.00000   0.2000000
> 0.0000    0.0000    1.000
> ------------------------------------------------------------------------------------------------------------------------------------------------
>
> Questions (forgive me if they are obvious but I'm really just starting)
>
> 1) How do I decide on the space group? With incommensurate structures is
> it
> always just P -1
>
> 2) Cen: IF I choose P -1 as the space group don't I have to set Cen to 2
> (i.e. centro-symmetric)
>
> 3)Laue: Is that the Laue symm of the the underlying crystallographic
> phase?
>
> 4)SYM and MSYM: Is there a way to create them or do I have to deduce them
> by
> the space group I choose. Because for P -1 I wouldn't expect a +1/2
> component in them (do they come from the Laue sym?). There is really not
> much about this in the FP manual
>
> 5) Atom types: Where in the manual do I find the correct types I have to
> use? Is it always just M in front of the atom?
>
> 6)Do I enter the propagation vectors just as I did it, or do I have to do
> something different?
>
>
> To whoever takes the time in answering even just a small number of these
> questions or giving any advice I am really thankful. I'm very intrigued by
> this magnetic neutron scattering business but it's sometimes hard to keep
> on
> top of all the arising issues.
>
> With best regards
> Alex
>


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