Comparison of rare earths doping (neodymium and samarium) on structural and magnetic properties of Ni–Zn–Bi nanoferrites

Excellent magnetic properties in ferrites are required for high-frequency applications and for wastewater treatment. Thus, the present study shows the comparison of magnetic and structural properties of Nd and Sm substituted Ni–Zn–Bi ferrites with the series Ni 0.5 Zn 0.5 Bi 0.04 Nd x Fe 1.96–x O 4 (with step size 0.002) and Ni 0.5 Zn 0.5 Bi 0.04 Sm x Fe 1.96–x O 4 (with step size 0.02) prepared using citrate precursor method. The impact of the substitution of rare earth ions (Nd and Sm) on magnetic properties of the synthesized samples is observed using a vibrating sample magnetometer (VSM). The saturation magnetization values enhance considerably from 52 to 58 emu/g for Nd 3+ ions and 39 to 57 emu/g for Sm 3+ ions, thus, making these materials magnetically hard. Further, the higher value of coercivity is also observed ranging from 133 to 167 Oe for Nd 3+ ions and 81 to 155 Oe for Sm 3+ ions. The shape of hysteresis loops indicates a super paramagnetic and ferromagnetic behavior in the obtained samples. The squareness ratio value is <0.5, suggesting the uniaxial anisotropy of particles and hence, these ferrites are suitable for microwave-absorbing and in permanent magnetic materials. The X-ray diffraction (XRD) pattern shows the formation of pure cubic crystallites, where, lattice parameters range from 0.840 to 0.839 nm and from 0.838 to 0.839 nm for Nd 3+ and Sm 3+ ions substitution, respectively. The crystallite size ranges between 28.63 to 29.89 nm and 18.33 to 26.23 nm, for substitution of Nd 3+ and Sm 3+ ions, respectively. Field emission scanning electron microscopy (FESEM) shows the formation of homogeneous grains, whereas, energy dispersive spectrometer (EDS) counts describe the purity of the samples. The Sm concentration x  = 0.10 has the maximum surface area with value of 42.6 m 2 /g which proves to be having good data storage application due to high surface area. The zero-field cooled (ZFC) and field cooled (FC) data show that Nd-doped Ni–Zn–Bi nanoferrites show superparamagnetic behaviour in the room temperature range which makes them suitable for practical applications.