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CoNdxFe(2−x)O4 (x = 0.0–0.05) spinel ferrites are successfully synthesized by mechanical milling using solid‐state reaction. The effects of Nd3+ ions on structural, microstructure, and magnetic and microwave‐absorbing properties of samples are analyzed. The X‐ray diffraction pattern shows a single‐phase cobalt ferrite for all compositions. Refinement of the structure shows that an increase in the concentration of Nd3+ ions leads to the structure parameter and volume of unit cell to decrease. Lattice strain arises in the crystal, and limiting the crystallite growth is confirmed from the Williamson–Hall analysis. The particle size of the doping samples decreases compared to that without doping. The magnetic parameters, namely coercivity field and saturation magnetization, are strongly affected by the insertion of Nd3+ ions. Another important role of Nd3+ ions is in tuning the performance of microwave absorption. The maximum reflection loss values are gradually increased from −12.65 dB (≈94.35% microwave attenuation) up to −28.57 dB (≈99.86% microwave attenuation) in the concentration of x = 0.0–0.05. Their effective bandwidth also shows an increase from 0.05 up to 1 GHz. The results exhibit that Nd3+ ion‐doped cobalt ferrite has potential properties in designing novel microwave‐absorbing materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • A single phase NiNd x Fe (2-x) O 4 were successfully synthesized by milling technique. • The particle size tends to decrease as the Nd atom content increases. • The Ms value was decreased when the Hc increased with increases in the Nd3+ ions. • The microwave absorption ability shows the enhancement with an increase Nd3+ ions. • NiNd x Fe (2-x) O 4 is a promising new material for microwave absorption. The neodymium substituted nickel ferrites with a nominal composition of NiNd x Fe (2-x) O 4 (with x = 0.00; 0.01; 0.03; 0.05; 0.06; 0.08 and 0.10) were successfully synthesized by milling technique. The NiO, Nd 2 O 3 and Fe 2 O 3 powders were used as raw materials and were prepared in a mole ratio. The characterization of the samples was done by X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA). In this study, the PXRD showed and verified that all Nd3+ ion successfully substituted the NiFe 2 O 4 samples with a single cubic spinel phase. Infrared spectra showed two strong absorption bands in the frequency range of 405–420 cm−1 and 595–610 cm−1, which were respectively attributed to tetrahedral and octahedral sites of the spinel ferrites. The SEM revealed homogenous morphology on all NiNd x Fe (2-x) O 4 but still not uniform powders. The particle size of the powder ranged from 150 to 700 nm. The magnetic properties of all of the samples showed a ferrimagnetic behavior. The Ms value was decreased when the Hc increased with increases in the Nd3+ substitution value. The ability to absorb the microwave measured by VNA shows the enhancement of the microwave attenuation where the Nd3+ substitution increased. The microwave attenuation changes increased from 91.25% to 98.32%. It can be seen that the composition of x at 0.05 promises to be new material for microwave absorption. [ABSTRACT FROM AUTHOR]

• The composite Co/Fe 2 O 3 /AC was achieved through a simple milling method at 10 Hz for 1 hour. • The 20% AC is excellent electromagnetic absorption with minimum RL -69.39 dB, thickness 4 mm at the frequency 11.302 GHz. • For 15% AC shows an RL value of -61.74 dB for the thickness of 3 mm at the frequency 11.19 GHz. • Carbon act as a net and capturing the big ball from the Co ion and Fe ion with a large radius compared with C atoms. • The EM hit atoms cobalt, iron, oxygen, and carbon, transfer energy resulting vibration the atoms and lattice. The new absorbing materials, thin, light, and strong become a challenge and attract more scientists to find excellent absorption performance. In this work, the composite Co/Fe 2 O 3 /AC was achieved through a simple milling method at 10 Hz for 1 h. The Co/Fe 2 O 3 /AC for 20%AC has an excellent absorption of electromagnetic wave performance with a minimum reflection loss (RL) value of −69.39 dB for the thickness of 4 mm at the frequency 11.302 GHz, followed by 15% AC with an RL value of −61.74 dB for the thickness of 3 mm at the frequency 11.19 GHz. The excellent absorption performance is related to conductivity loss, multiple reflections, electron hoping, and scattering caused by the unique arrangement of atoms. The study provided new and high potentials composite for the development of electromagnetic wave absorbing materials. [ABSTRACT FROM AUTHOR]