We will study the changes in the crystal structure and magnetic structure in FeAs as a function of doping with cobalt at low temperatures. Cobalt replaces iron and the helimagnetic antiferromagnetic structure of FeAs which is stable up to 3% cobalt doping will be determined using neutron powder diffraction using WISH. We will combine these structural studies with muon spectroscopy and magnetrometry and single crystal resonant x-ray diffraction o obtain a detailed and comprehensive picture of how the magnetic interactions are altered by doping. This study will provide insights into the behaviour of iron pnictides which display superconductivity under doping.