[en] This paper reports on the effects of Bi₂O₃ and Co on the magnetic properties of Li_0.50Fe_2.50O₄ ceramics. The magnetic properties (static permeability) of the lithium ferrite ceramics with low concentration of Bi₂O₃ (0.2% and 0.5%), as a function of sintering temperature, can be explained by the magnetic circuit model, while those of the samples with high concentration (1-5%) are in a good agreement with the Globus model. Both models are not applicable to the results of pure Li_0.50Fe_2.50O₄ samples, because their magnetic properties are determined by both the density and grain size. Further modification of Li_0.50Fe_2.50O₄ with Co makes it possible to produce ferrite ceramics with promising magneto-dielectric properties. Maximum static permeability is observed in Li_0.50-0.50xCo_xFe_2.50-0.50xO₄ at x = 0.01, which can be qualitatively explained by magnetocrystalline anisotropy and ion ordering induced local uniaxial anisotropy. It is found that the Li_0.50-0.50xCo_xFe_2.50-0.50xO₄ (with x = 0.030-0.035) ceramics sintered at ≤950 deg. C have matching permeability and permittivity of 13-15, as well as sufficiently low magnetic and dielectric loss tangents of ≤10^-2, over 3-30 MHz (HF band). From the laws of physics, HF antennas can be physically reduced by a factor of 13-15, with unchanged electrical dimension, if loaded with this class of magneto-dielectric materials