EMI Cores KEMET EMI Cores provide high-frequency noise suppression in electronic circuits. There are two ferrite material options for KEMET EMI Cores, namely Nickel-Zinc (NiZn) and Manganese Zinc (MnZn). The NiZn core material is typically effective for theMHz band range (FM-band frequencies), whereas the MnZn core material is typically effective for the kHz band range (AM-band frequencies). The MnZn core material offers a lower resistance compared to the NiZn and hence adequate insulation is required before use (recommended to measure the actual frequency-range effectiveness in the target application). The effective frequency range varies depending on core shape, size, and the number of turns.