We studied the complex permittivity and permeability properties of magnesium-copper spinel ferrite under various heat-treatment conditions. We simulated two types of materials: dielectric and magneto-dielectric. Dielectric materials show the miniaturization of the antenna; however, decreases of bandwidth and efficiency are observed. Magneto-dielectric materials show the capability of improvement of bandwidth and efficiency with a miniaturization of the antenna. The target properties were established from simulated results of permittivity and permeability <10, and permittivity/permeability □ 1. Magnesium spinel ferrite was shown to increase the permittivity (from 7 to 11.7) and the permeability (from 5.5 to 8.2) with an increase of sintering temperature (from 1,150℃ to 1,350℃). However, the high sintering temperature (1,350℃) affected the increase of permittivity more than it did the permeability, and this condition deteriorated the ratio, loss, and resonance frequency. These problems were overcome with the substitution of copper (of formula Mg0.9Cu0.1Fe2O4), the addition of a sintering agent (alginate 1 wt%), and the condition of a lower sintering temperature (1,250℃). The new conditions showed equal value (□ 9.5) of the permittivity and permeability.