of the magnetic structure can be very simple,
a set of moments in P1, so setting understanding
what it all means is quite unambiguous.
FullProf has a k vector and is far more flexible in the ways in which
magnetic structures can be defined. This flexibility can make it hard to set
up a magnetic phase. SARAh -Refine tries to deal with most of these problems
for you (see the video help for the entire process), but it is sometimes
less obvious to see what is happening in the pcr file.
If you have any questions, feel free to get in contact. Good luck!
Andrew
ps/ to see the SARAh documentation- install SARAh (which contains
SARAh-Representational Analysis and SARAh-Refine) on a windows computer
(including macs with parallels or vmfusion), and look in the help menu
On 23 Jul 2009, at 12:27, Alexander Barcza wrote:
Dear Ross,
Thanks for your reply. Sorry for being so exclusive in my initail mail, of
course I should have included everyone! The title of PhD student also
applies to me.
I've seen a talk about SARAh by Andrew Wills at ISIS and was impressed by
it. Therefore I've already downloaded it but didn't succeed in using it yet.
The problem is actually already at the beginning:
In my GSAS file I created a second phase with P1 and just copied the atoms
of the main phase over.
I loaded that file by clicking GSAS Controls, Load GSAS EXP file
How do I then define the MAT file?
Sorry, it must be obvious but I can't find it. I am happy to read some
documentation but couldn't find any on the website (
http://www.chem.ucl.ac.uk/people/wills/index.html).
Thanks again for your help
Alex
2009/7/23 Ross H Colman ucca...@ucl.ac.uk
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 FurthATZ Nvk More
2 0 0 -1-1 0 0 0. 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
! Pr1Pr2Pr3 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 31
!
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 VekXYZ Biso Occ Rm
Rphi Rtheta
! Im Iphi Ithetabeta11 beta22 beta33 MagPh
Co1 MCO2 1 1
