Investigation on the structural, optical, and magnetic features of Dy 3+ and Y 3+ co-doped Mn 0.5 Zn 0.5 Fe 2 O 4 spinel ferrite nanoparticles

Dy 3+ and Y 3+ ions co-doped Zn 0.5 Mn 0.5 Fe 2 O 4 (ZMDyYFe) (x   =   0.00–0.05) nanospinel ferrite nanoparticles (SFNPs) have been synthesized through an ultrasonication approach. The rare earth co-doping with Dy 3+ and Y 3+ ions was applied to tune the structural and magnetic properties of the ZnMn spinel ferrites. The influence of the co-doped of both Dy 3+ and Y 3+ ions on the structural, optical, and magnetic characteristics of Zn 0.5 Mn 0.5 Fe 2 O 4 SFNPs was analyzed in detail by X-ray diffractometry (XRD), scanning electron microscopy (SEM), high- resolution tunneling electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), and elemental mappings. XRD results revealed the formation of the spinel phases and the structural changes which were accompanied the Dy 3+ and Y 3+ ions co-doping. The cubic spinel phase of all samples has been confirmed by the application of Rietveld refinement. As the value of `` x `` increased up to x  = 0.04, the lattice constant was found to increase from 8.401 to 8.408 Å and the size of the crystallites was calculated to be in the range 7.26 nm-11.10 nm. HR-SEM and HR-TEM micrographs also presented the cubic morphology of the products. Diffuse reflectance spectroscopy (DRS) measurements were done on pure and Dy 3+ and Y 3+ co-doped Mn 0.5 Zn 0.5 Fe 2 O 4 SFNPs. Direct band gaps ( E g ) were extracted from Tauc plots. E g values existed in a narrow range between 1.64 eV and 1.74 eV. Magnetic investigations exhibited the superparamagnetic behavior at RT (room temperature) and ferrimagnetic behavior at 10 K for synthesized samples. At RT analyzes, undoped Mn 0.5 Zn 0.5 Fe 2 O 4 SFNPs had the maximum saturation magnetization ( M S ) of 34.84 emu/g and magneton number ( n B ) of 1.47 μ B. An inverse proportion with the increasing ion ratio were observed among those parameters. The 10 K magnetization data revealed that co-doped Mn 0.5 Zn 0.5 Dy 0.02 Y 0.02 Fe 1.96 O 4 SFNPs had magnetic parameters of M S,max = 67.39 emu/g, n B,max  = 2.88 μ B and H C,max  = 574 Oe ( H C : coercivity and max: maximum). Among the rest of the co-doped samples, M S and n B data had a similar negative trend with respect to the increasing ion ratio including the remnant magnetizations ( M r ). The rest of the H C values were found to be between 275 Oe and 361 Oe. Squareness ratios (SQRs= M r /M S ) had a range of 0.181- 0.321 and confirmed the multi-domain wall structure for all SFNPs at 10 K. The maximum value of effective crystal anisotropy constant ( K eff ) 6.04 × 10 4 Erg/g belongs to Mn 0.5 Zn 0.5 Dy 0.02 Y 0.02 Fe 1.96 O 4 SFNPs, and others have the same order of 10 4 Erg/g for K eff constants. Although this sample has the largest internal anisotropy field ( H a ) of 1794 Oe, it can also be classified as a soft magnetic material like other nanoparticle samples. The Dy 3+ and Y 3+ ions co-doped ZMDyYFe (x   =   0.00–0.05) SFNPs, with varying structural and magnetic properties, can have potential applications in various areas such as magnetic switching, security, magnetic core, microwave absorption applications, nanofabrication and nanodevices.