Enhanced Magnetic and Microwave Absorbing Properties of Nd³⁺ Ion Doped CoFe₂O₄ by Solid‐State Reaction Method

Abstract

Research on spinel ferrite is a state-of-the-art and rapidly developing field because this material has attractive electrical and magnetic properties and also exhibits different behavior compared to its bulk form. The general formula for the spinel ferrites material is AB 2 O 4 (A ¼ ion of metal transitions such as Co, Mn, Ni, Zn, and Cu; B ¼ trivalent ion of Fe). The A would occupy the tetrahedral site, and B would occupy the octahedral site of the fcc crystal system. [1,2] One of the spinel ferrites that have a prominent property is cobalt ferrites. The cobalt ferrites possess good properties, namely high permeability due to high saturation magnetization, nonconductive (high resistivity), better chemical stability, and high magnetostriction coefficient. [3][4][5][6] Due to its excellent magnetic characteristics, cobalt ferrite can be used in magnetic storage and microwave devices. In addition, this material is a promising candidate as a magneto-optical recording media and a microwave or RADAR absorbing material because it is chemically stable, has a medium mechanical hardness, and the first-order anisotropy constant has a large positive value. [5][6][7] According to Panda, who has studied the electric transport behavior of nano cobalt ferrite, it shows that the main contributor that affects the conductivity and dielectric properties of materials is the conduction between grain boundaries and surface polarization, while the value of the dielectric constant is determined by the exchange of electrons and holes between Co 3þ -Co 2þ and Fe 2þ -Fe 3þ . [8] Routray also reported that in general the ferroelectric properties of a material are influenced by its compound composition, material homogeneity, crystal defects, and domain orientation. [9] In addition, it was stated that grain size also plays an important role in polarization and ferroelectric behavior. This is related to the presence of an intrinsic conduction mechanism of the magnetic compound and is compatible with its ferroelectric response. According to him, in general, this material has a high conductivity value due to the presence of oxygen vacancy in the polaron mechanism because Fe 2þ and Fe 3þ are present simultaneously. Likewise, according to Chithra that magnetic properties are influenced by changes in ionic magnetic moments, distribution of cations in the lattice, ionic anisotropy, and structural changes in this cobalt ferrite nanomaterial. [10] The requirements for microwave absorbing material must have high permeability and permittivity. [11] The magnetic and dielectric properties of CoFe 2 O 4 can be modified through the substitution of

Effects of Nonmagnetic Zn2+ Ion and RE Ion Substitution on the Magnetic Properties of Functional Nanomaterials Co1−yZnyRExFe2−xO4 (RE = La, Sm, Gd) by Sol–Gel

“…The coercivity decreases with increasing lanthanum content, which can be due to the weakening of anisotropy when the Co 2+ ions migrate to the tetrahedral site. While x = 0.05 and x = 0.10, the coercivity has no significant changes, which may be attributed to the appearance of impurity phases LaFeO3 [47,49,50].…”