### Syntax

[~, coeff, s] = sw_mff(atomname)

[formfactval, coeff, s] = sw_mff(atomname,Q)

### Description

[~, coeff, s] = sw_mff(atomname) returns the magnetic form factor coefficients for the magnetic atom identified by a string, e.g. 'MCR3'. The function reads the magion.dat file for the stored form factor coefficients.

[formfactval, coeff, s] = sw_mff(atomname,Q) also calculates the form factor values at the given $$Q$$ points (in Å$$^{-1}$$ units.

The source of the form factor data are:

1. A.-J. Dianoux and G. Lander, Neutron Data Booklet (2003).
2. K. Kobayashi, T. Nagao, and M. Ito, Acta Crystallogr. A. 67, 473 (2011).

### Input Arguments

atomName
String, contains the name of the magnetic ion in FullProf notation (e.g. for Cr^{3+} use 'MCR3' or 'Cr3'). It can be also a vector of the 7 form factor coefficients. If the string contains whitespace, the first word will be used as input. Can be also a cell of strings to calculate coefficients for multiple ions.
Q
Momentum transfer in Å$$^{-1}$$ units in a matrix with dimensions of $$[1\times n_Q]$$ or $$[3\times n_Q]$$.

### Output Arguments

formFactVal
Value of the form factor, evaluated at the given $$Q$$ points.
coeff
Form factor coefficients according to the following formula: $\langle j_0(Q_s)\rangle = A\exp(-a\cdot Q_s^2) + B\exp(-b\cdot Q_s^2) + C\exp(-c\cdot Q_s^2) + D\exp(-d\cdot Q_s^2) + E$

where $$Q_s = \frac{Q}{4\pi}$$ and $$A$$, $$a$$, $$B$$, … are the coefficients. The $$D$$ and $$d$$ coefficients can be zero.

S
Value of the spin quantum number (read from the spin column in magion.dat).