Investigation of magnetic ordering and cation distribution in the spinel ferrites CrxFe3−xO4 (0.0≤x≤1.0)

Magnetic moment directions and distributions of cations in Cr (Co) substituted spinel ferrites Ni0.7Fe2.3O4

“…16,17 In the synthesis process, AR Grade nitrates or chlorides (see below for details) in the stoichiometric ratios appropriate for each value of x were dissolved in deionized water with stirring at a constant temperature of 343 K. Precipitates were formed with the slow addition of a 1.1 molar sodium hydroxide solution, with stirring, over a period of 40 min, to adjust the pH value of the solutions to about 11-12. The precipitates were washed several times with deionized water in order to remove residual Cl − , NO 3 − and Na + ions from the solutions, and then filtered.…”

“…As in our previous work, [16][17][18][19][20][21][22] the cation distributions for all the samples were estimated by fitting the dependence of the magnetic moments measured at 10 K on the doping level, using the quantum mechanical potential barrier model proposed by our group. [26][27][28][29] In the fitting process, the following factors were taken into account:…”

“…6,7 The influence of Cr-doping on the crystal structure and physical properties of spinel ferrites have been reported in many studies, but the Cr ion distributions have been disputed. [8][9][10][11][12][13][14][15] Pervaiz et al 8 In order to explain these discrepancies, our group proposed an O2p itinerant electron model, [16][17][18][19][20][21][22][23] which contains three factors: (i) There are O2p holes in the outer orbits of oxygen anions. 24 In a given sublattice, an O2p electron with constant spin direction can hop to the O2p hole of an adjacent oxygen anion with a metal cation acting as intermediary.…”

“…(iii) The two oxygen O2p electrons which have opposite spin directions become itinerant electrons in the two different sublattices (involving the (A) or [B] sites). Using these premises, our group has successfully fitted the magnetic moments, measured at 10 K, of ferrite samples of Cr x Fe 3−x O 4 (0.0 ≤ x ≤ 1.0), 16 Cr x Ni 1−x Fe 2 O 4 (0.0 ≤ x ≤ 0.3), 17 Cr x Co 1−x Fe 2 O 4 (0.0 ≤ x ≤ 1.0), 18 Cu x1 Cr x2 Fe 3−x1−x2 O 4 (0.0 ≤ x 1 ≤ 0.284 with 1.04 ≤ x 2 ≤ 0.656), 19 Ni 0.68−0.8x Ti x Fe 2.32−0.2x O 4 (0 ≤ x ≤ 0.312), 20 and Mn x Co 1−x Fe 2 O 4 (0.0 ≤ x ≤ 0.3) 21 and estimated the cation distributions for all samples, using the quantum mechanical potential barrier model (QMPB) also proposed by our group. [26][27][28][29] In the fitting process, only one independent fitting parameters, V BA (M 2+ ), was used for a given sample.…”

“…The results indicate that the distributions of the Cr cations at the (A) and [B] sites are very close to those obtained using neutron diffraction and are very close to those of Fe cations. For the three series of samples in this work and the samples M x N 1−x Fe 2 O 4 (M, N = Cr, Mn, Fe, Co, and Ni) in our previous work, [16][17][18][19][20][21][22] we have found that the pattern followed by the fitting parameter V BA (M 2+ ) is similar to that of the third ionization energy of the M cation, whether the initial value of V BA (M 2+ ) was assumed to be proportional to the second or third ionization energy of the M cation.…”