Spinner
thanks its existence to the geometrically frustrated
magnets in the mineral family of the jarosites. The first versions of
the program (then called spinner) were running by the end of 2005. In
August 2007 a first version (V. 1) of the program was publised on
www.ccp5.ac.uk . For submission to sourceforge the name had to be
changed, the name 'spinner' was already in use. Hence, the 'S' has
been replaced by a 'C', which should not make too much of a
difference for the sound of the name. The 'C' can also be taken to
stand for 'classical'.
The hope was that using a Monte Carlo program different models for the magnetism in in particular potassium iron jarosite and hydronium iron jarosite could be studied numerically. Potassium iron jarosite (KFe3(OH)6(SO4)2) freezes at 65 K into a non-collinear antiferromagnetic structure, due to either a single-ion anisotropy of easy-plane character or due to Dzyaloshinski-Moryia interactions. Hydronium jarosite on the other hand (K -> H3O) freezes into a glassy state below 17~K. What is the origin of the marked difference in the magnetic groundstate of these two systems which nearly the same magnetic structure is still an open question.