(spinw-coupling)=

# spinw.coupling property

## Sub fields
 
`dl`
: Distance between the unit cells of two interacting
  spins, stored in a $[3\times n_{coupling}]$ matrix.
 
`atom1`
: First magnetic atom, pointing to the list of
  magnetic atoms in the list generated by `spinw.matom`, stored in a
  row vector with $n_{coupling}$ element.
 
`atom2`
: Second magnetic atom, same as `atom1`.
 
`mat_idx`
: Stores pointers to matrices for every coupling in a
  $[3\times n_{coupling}]$ matrix, maximum three matrix per
  coupling (zeros for no coupling) is allowed.
 
`idx`
: Neighbor index, increasing indices for the equivalent
  couplings, starting with 1,2,... which means first and second
  neighbor bonds, respectively.
 
`type`
: Type of coupling corresponding to `mat_idx` matrices.
  Default is 0 for quadratic exchange, `type = 1` for
  biquadratic exchange.
  
`sym`
: If `true` the bond symmetry operators will be applied
  on the assigned matrix.
  
`rdip`
: Maximum distance until the dipolar interaction is
  calculated. Zero value means no dipolar interactions
  are considered.
  
`nsym`
: The largest bond `idx` value that is generated
  using the space group operators. Typically very long bonds for
  dipolar interactions won't be calculated using space group
  symmetry.