## 1 Introduction  
Technological advances and rapid proliferation of wireless gadgets that operate at super high frequency range have led to the continuous rise in electromagnetic (EM) interference with electronic equipment, likewise EM pollution that endangers human health [1]. For instance, it has been reported that the long exposure of human to EM radiation could increase morbidity, particularly in pregnant women and children [2]. Fabrication of EM wave absorptive materials which can dissipate the undesirable EM energy have been widely explored as an effective way to tackle this problem [3, 4]. The desired features of an efficient microwave absorbing materials (MAM) includes strong absorption, light-weight, wide operating bandwidth, thin thickness, and low cost [5]. Magnetite (Fe\({}_{3}\)O\({}_{4}\)), a member of the spinel class of ferrite is endowed with excellent complex permeability and permittivity, which are significant governing parameters in EM wave absorption. In addition, it possesses high magnetization saturation (Ms) at ambient temperature, high Curie temperature and low production cost which attracted much interest in the field of EM wave absorption. However, Fe\({}_{3}\)O\({}_{4}\) as an absorptive material have some limitations such as the rapid decrease in permeability value at microwave frequency, large density, ease of oxidation and mismatch of impedance which impedes its performance as an ideal MAM [6; 7]. Recently, several research efforts have been geared towards improving the microwave absorption performance (MAP) of Fe\({}_{3}\)O\({}_{4}\). For example, [PERSON] et al. [8] fabricated hollow Fe\({}_{3}\)O\({}_{4}\) nanoparticles via solvothermal route, with the aim of reducing its density while retaining good magnetic properties for efficient MAP. They established improved EM wave absorption with increasing particle size and change in morphology. Maximum EM absorption with RL value of \(-\)55.14 dB at 11.76 GHz was achieved with an absorber thickness of 2.07 mm. [PERSON] et al. [9] synthesized nano-Fe\({}_{3}\)O\({}_{4}\) by an innovative wet chemical route, employing hydrazine hydrate as anti-oxidation agent. The synthesized Fe\({}_{3}\)O\({}_{4}\) nanoparticle of average diameter of 77 nm possessed high magnetization saturation and coercivity value of 72.36 emu/g and 95 Oe, respectively. The minimum RL value of \(-\)21.2 dB was achieved with 6 mm thickness. Similarly, optimization of the MAP of Fe\({}_{3}\)O\({}_{4}\) via design and fabrication of hierarchical nanostructure have also been explored. [PERSON] et al. [10] exploit one-step and template-free synthesis method to prepare octahedral Fe\({}_{3}\)O\({}_{4}\) nanostructure by direct decomposition of an iron organic compound with molten salt. The sample annealed at 800 \({}^{\circ}\)C displayed maximum EM absorption of \(-\)23.67 dB at 15.24 GHz at a thickness of 1.4 mm. The enhanced microwave absorption (MA) at a thin thickness (1.4 mm) was attributed to the morphology, proper attenuation value, and good impedance matching. [PERSON] et al. [11] prepared flower-like Fe\({}_{3}\)O\({}_{4}\) with porous nanostructures which displayed enhanced MAP, with minimum RL value of \(-\)28.3 dB achieved with 2 mm thickness. Highly efficient MAM is required to possess high absorption at a thin thickness and low density for practical application. Herein, citric acid coated Fe\({}_{3}\)O\({}_{4}\) (C-Fe\({}_{3}\)O\({}_{4}\)) was prepared by facile co-precipitation method and embedded in polyvinylidene fluoride (PVDF) matrix by an in situ solvent mixing technique. This was proposed with the aim of achieving high absorption coefficient at a reduced density and thickness without the design of a complex hierarchical structure. The Fe\({}_{3}\)O\({}_{4}\) was coated with citric acid to introduce carboxyl and hydroxyl functional groups. It has been reported that the presence of these functional groups within an absorptive material can provide additional polarization centers to enhance the EM wave absorption [12].