Magnetic moments of Ti cations in Ti-doped Ni0.68Fe2.32O4 spinel ferrites

Antiferromagnetic coupling between Mn3+and Mn2+cations in Mn‐doped spinel ferrites

“…In the following, this assumption is referred to as the “constraint from Hund's rules.” This kind of antiferromagnetic structure has been observed by our group. For example, an antiferromagnetic structure in which the magnetic moments of Ti 2+ (3d 2 ) and Ti 3+ (3d 1 ) cations are antiparallel to those of divalent and trivalent Fe and Ni in a given sublattice, was observed by magnetic measurement in two series of Ti‐doped Ni 0.68 Fe 2.32 O 4 ferrite samples . Likewise it was observed in infrared spectra of M Fe 2 O 4 ( M = Fe, Co, Ni, Cu, and Cr) ferrite samples that the magnetic moments of Cr 2+ (3d 4 ) cations are antiparallel to those of Fe 2+ (3d 6 ) cations in the [B] sublattice .…”

“…In order to explain these puzzles, and considering the fact that the spin directions of 3d electrons in the cations are constrained by Hund's rules and that the spin direction of the itinerant electrons is constant, our group proposed that the magnetic moment directions of the cations with 3d electron number n d ≤ 4 (such as Ti 2+ , Ti 3+ , Cr 2+ , Cr 3+ , and Mn 3+ ), are antiparallel to those of the cations with n d ≥ 5 (such as divalent and trivalent Fe, Co, Ni, and Cu) whether at the (A) sites or at the [B] sites of the spinel ferrites . In the following, this assumption is referred to as the “constraint from Hund's rules.” This kind of antiferromagnetic structure has been observed by our group.…”

Valence of Ti cations and its effect on magnetic properties of spinel ferrites TixM1−xFe2O4(M = Co, Mn)

“…Spinel ferrites Ti x Co 1Àx Fe 2 O 4 (0.0 # x # 0.4; hereaer referred to as the Co-series) and Ti x Mn 1Àx Fe 2 O 4 (0.0 # x # 0.3; here-aer referred to as the Mn-series) were prepared using the method of solid-phase reaction. 17 The analytical reagent (AR)grade chemicals CoO, MnO 2 , Fe 2 O 3 , and TiO 2 were used as the starting materials. First, stoichiometric amounts of each chemical were mixed together, ground for 8 h in an agate mortar, and then calcined at 1173 K for 5 h. The calcined materials were then ground again for 1 h. The ground powder was calcined at 1473 K for an additional 5 h, and then further ground for 1 h. Next, the twice calcined and thrice ground powder was pressed into pellets at a pressure of 10 4 kg cm À2 and then sintered at 1673 K for 10 h in a tube furnace under an argon ow.…”

“…15 However, when Kale et al prepared Ti x Ni 1+x Fe 2À2x O 4 (0.0 # x # 0.7), they estimated the cation distribution at the (A) and [B] sites using X-ray diffraction and came to the conclusion that the fraction of Ti 4+ cations entering the (A) sites increased with increasing x, and it reached 0.5 when x ¼ 0.7. 16 In order to resolve these discrepancies regarding cation distributions in spinel ferrites, Xu et al investigated the valence, distribution of cations and the magnetic structure of Ti-doped spinel ferrites [17][18][19] by using an O 2p itinerantelectron model. [20][21][22] They found an additional antiferromagnetic phase when Ti cations replaced a portion of the Ni or Fe cations in the spinel ferrites Ni 0.68 Fe 2.32 O 4 (ref.…”

Effects of NiO addition on the microstructure, elemental distribution and magnetic properties of Mn–Zn power ferrites

“…Recently Mn-Zn power ferrites has been widely investigated and different kinds of additives such as CaO, Nb 2 O 5 , In 2 O 3 , ZrO 2 , TiO 2 , Co 2 O 3 , Ta 2 O 5 and Eu 2 O 3 have been used for improving their properties [4][5][6][7][8][9][10][11][12]. Wang et al [5] investigated the effects of SiO 2 , CaO, TiO 2 , and Nb 2 O 5 additives on the densification, microstructural evolution, and high-frequency magnetic properties of Mn-Zn ferrites.…”