Influence of Zinc Doping on the Structural and Magnetic Properties of Ni-Ga-Sm Polycrystalline Ferrites

Abstract

Polycrystalline Ni 1−x Zn x Fe 1.49 Ga 0.5 Sm 0.01 O 4 (0 ≤ x ≤ 0.5) spinel ferrite powders were prepared using standard ceramic method. Structural and magnetic properties of the sintered samples were investigated using X-ray powder diffraction, Mössbauer effect spectroscopy, and vibrating sample magnetometer. X-ray analysis confirmed the formation of single phase cubic spinel ferrites for all samples. The cation distribution obtained from the Mössbauer effect measurements suggested that Sm 3+ ions substituted iron in the octahedral [B] site and increase the magnetism in the studied samples. On the other hand, Ga 3+ ions replaced iron in both tetrahedral (A) sites and octahedral [B] sites. For x ≤ 0.3, Zn 2+ ions are introduced to (A) sites and unusually for higher Zn content, x > 0.3, they distribute in both (A) and [B] sites and suppress magnetism in this system. The cation distribution obtained from the Mössbauer effect measurements explains well the change in the values of both lattice parameter (a) and the saturation magnetization (M s ).

Synthesis and Characterization of Ultrasmall Nanocrystalline Zn-substituted Ni-Sm-Ga Ferrites

“…2 and Table 1. The lattice parameter (a) values are very close to the values observed for the bulk samples [3]. From Table 1, a initially increases up to x = 0.3 and then decreases for higher Zn content.…”

“…For x ≥ 0.3, Zn 2+ ions unusually distributed in both A to B sites. Recently, the standard ceramic method was used to prepare Ga-, Zn-, and Sm-doped Ni 1−x Zn x Fe 1.49 Ga 0.5 Sm 0.01 O 4 (0.0 ≤ x ≤ 0.5) samples [3]. Our measurements confirmed that Sm 3+ ions favor the B sites and support magnetism in the studied system.…”

“…Only for x > 0.3, Zn 2+ distributes between A and B sites. Depending on these changes in the cation distribution and the differences in the ionic radii of Fe 3+ , Ga 3+ , Zn 2+ , and Ni 2+ , the behavior of the lattice parameter was explained [3]. For the present nanoparticles, it is difficult to determine the cation distribution for Zn doped samples from the ME measurements since the ME spectra are relaxed and contains only a doublet and a singlet for x = 0.3 and x = 0.5 samples as discussed in the next section.…”

“…This might indicate that every particle is formed by the agglomeration of a small number of crystallites or grains [22]. Table 2 Interatomic bond lengths between the cation-anion (p, q, r, and s) and between the cations (b, c, d, e, and f ) Figure 5 shows Mössbauer effect spectra for NiFe 1 [3]. In nanoparticles, the magnetic anisotropy energy is proportional to the volume, and for very small particles, it may therefore be comparable to the thermal energy.…”

“…The magnetic properties of these inverse spinel ferrites are governed by the chemical composition and the method of preparation. Altering the chemical composition is achieved by doping nickel ferrites with different transition metals and rare earth (R) ions [1][2][3]. Both the type of the dopant and its amount are critical in changing the cation distribution and consequently the properties of the doped Ni-ferrite [1,2].…”