At CERN, the circulating beam current measurement is provided by two types of transformers, the DC Current Transformer (DCCT) and the Fast Beam Current Transformer (FBCT). Each transformer is built based on toroidal cores made from a magnetic material. Depending on the type of measurement to be performed these cores require different magnetic characteristics for parameters such as permeability, coercivity and the shape of the magnetization curve. In order to study the effect of changes in these parameters on the current transformers, several interesting raw materials based on their as-cast properties were selected. The materials have been characterised to determine a suitable annealing processes to tailor their properties. As-cast properties such as the permeability, coercivity and Barkhausen noise have also been measured to enable the study of the effect of thermal treatment in the microstructure of the alloys, and the correlation of this with the change in the magnetic properties. The comparison of the measured properties have narrowed down the best materials for further study.