quantum-espresso/test-suite/tddfpt_magnons_fe/Fe.tddfpt_pp_magnons.in

 &lr_input
   prefix = 'Femag',
   outdir = './out',
   magnons = .true.,
   units = 3,
   itermax0 = 150,
   itermax = 150,
   extrapolation='no',
   epsil = 0.5,
   ipol = 2,
   start = 1780.0d0,
   increment = 0.1d0,
   end = 1820.0d0
 /