### 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:

- A.-J. Dianoux and G. Lander, Neutron Data Booklet (2003).
- 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).