Structural, magnetic, optical properties and cation distribution of nanosized Co 0.7 Zn 0.3 Tm x Fe 2-x O 4 (0.0 ≤ x ≤ 0.04) spinel ferrites synthesized by ultrasonic irradiation.

This study expressed the influence of Tm substitution on the structural, optical and magnetic properties of Co-Zn spinel ferrites (Co _0.7 Zn _0.3 Tm _x Fe _2-x O ₄ (0.0 ≤ x ≤ 0.04)). The different compositions were synthesized by sonochemical method using Qsonica ultrasonic homogenizer, frequency: 20 kHz and power: 70 W for 60 min. XRD patterns proved the presence of single-phase spinel ferrites with crystallites size in the 8-10 nm range. Cation distribution approved the occupancy of octahedral (B) site by Tm. The morphology and the elements stoichiometry are obtainable through FE-SEM, EDX and elemental mapping. Optical band gap (E _g ) values were estimated via DR % (percent diffuse reflectance) investigations and Kubelka-Munk theory. Tauc plots revealed that direct E _g values are ranging between 1.49 and 1.68 eV. The analyses of magnetization versus magnetic field, M(H), were performed. The following magnetic parameters like saturation magnetization M _s , squareness ratio (SQR = M _r /M _s ), magnetic moment n _B , coercivity H _c and remanence M _r have been evaluated. M(H) curves revealed the superparamagnetic (SP) at RT and ferromagnetic property at 10 K. It was showed that the Tm ³⁺ substitutions significantly affect the magnetic properties of host spinel ferrites. An increasing trend in the M _s , M _r , H _c , and n _B values was noticed for lower Tm ³⁺ substitution content.
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