Characterization of ferrites at low temperature and high frequency

Complex values of dielectric permittivity and magnetic permeability of 10 different materials, ferrites and ceramics, are measured in a frequency range from 1 to 40 GHz at room temperature and at 80 K. Recommendations are done for material usage in a cryogenic load for higher-order modes in the superconducting RF cavities of the Energy Recovery Linac.