Microwave absorbing materials (MAMs) has been intensively investigated in order to meet the requirement of electromagnetic radiation control, especially in S and C band. In this work, FeCo-based magnetic MAMs are hydrothermally synthesized via a magnetic-field-induced process. The composition and morphology of the MAMs are capable of being adjusted simultaneously by the atomic ratio of Fe²⁺ to Co²⁺ in the precursor. The hierarchical magnetic microchain, which has a core-shell structure of two-dimensional Fe_xCo_1−xOOH nanosheets anchored vertically on the surface of a one-dimensional (1D) Co microchain, shows significantly enhanced microwave absorption in C band, resulting in a reflection loss (R_L) of lower than −20 dB at frequencies ranging from 4.4 to 8.0 GHz under a suitable matching thickness. The magnetic coupling of Co microcrystals and the double-loss mechanisms out of the core-shell structure are considered to promote the microwave attenuation capability. The hierarchical design of 1D magnetic MAMs provides a feasible strategy to solve the electromagnetic pollution in C band.

Partially inverse spinel CoFe₂O₄, which may be prepared through various heat treatments, differs remarkably from the ideal inverse spinel in many properties. The structure of partially inverse spinel CoFe₂O₄ as well as its electronic and magnetic properties through a systemic theoretical calculation of (Co_1−x Fe _x )_Tet(Co _x Fe_2−x )_OctO₄ (x = 0, 0.25, 0.5, 0.75 and 1.0) have been investigated by the generalized gradient approximation (GGA) + U approach. It is found that the Co and Fe ions prefer their high spin configurations with higher spin moments at octahedral sites in all the studied cases, in line with experimental observations. The Co ions at the octahedral sites favour being far away from each other in the partial inverse spinels, which also show half metallicity at certain inversion degrees.