Magnetic studies of Bi x Y3-x Fe5O12 fabricated using conventional method

A series of Bi substituted yttrium iron garnet (Bi-YIG) nanoparticles with nominal formula of BixY3 − xFe5O12 in which x varied in steps of 0.0, 0.25 and 0.5 are prepared by conventional method. Vibration sample magnetometer (VSM) at Room temperature (RT) shows saturation magnetization decreases from 27.4 to 25.2 (emu/g) as x value increases from 0.0 to 0.5. Room temperature 57Fe Mössbauer spectra are recorded for these series. The hyperfine field value for octahedral and tetrahedral of samples increases from 484 and 390 kOe to 491 and 397 kOe respectability, as Bi replaces Y in (BixY3 − xFe5O12) atom with increasing x value. The effect of Bi3 +  substitution for Y3 +  on lattice constants, morphology and magnetic properties of pure YIG has been investigated

The correlation of lattice constant with superexchange interaction in Bi-YIG fabricated by mechanochemical processing

Magnetic and structural properties of Bi substituted YIG with nominal formula of Bi x Y3 − x Fe5O12 (x = 0.0, 0.25, 0.5, 0.75, 1.00) prepared via Mechanochemical Processing (MCP) have been studied with Mossbauer spectroscopy, X-ray diffraction (XRD). The temperature dependence of sublattice magnetic hyperfine field for samples is analyzed. The a–d intersublattice superexchange found to be antiferromagnetic and increases from − 21.97 to − 25.79 kB as Bi increases from 0.0 to 0.25. The a–a and d–d intrasublattice exchanges for sample x = 0.0 are 13.18 and 10.55 kB respectively while for sample x = 0.25 a–a and d–d intrasublattice exchanges are 7.7 and 8.9 kB respectively. The correlation of lattice constant and superexchange interaction are discussed

Atomistic and <i>ab initio</i> DFT modelling of the defect structures in Al³⁺/Cr³⁺-doped and co-doped Y₃Fe₅O₁₂

The defect structures when Y3Fe5O12 is doped with either Al3+ or Cr3+, and evenly co-doped with both, which have been a matter of controversy in the literature, are modelled using atomistic and ab initio DFT methods. When Y3Fe5O12 is doped with Al3+, the defect reaction energy obtained marginally favors the preferential substitution of Al3+ for Fe3+ at the tetrahedral sites as opposed to octahedral ones. This is indicative that for Al3+-doped samples processed at elevated temperatures, or containing undetected impurities, the substitution of Al3+ for octahedral Fe3+ is likely. To model the defect structure of the Cr3+ -doped Y3Fe5O12, it was essential that the Cr3+ ions crystal field stabilization energy (CFSE) and the Fe3+-O2-- Cr3+ spin-spin coupling derived from the ab initio DFT calculations ,be taken into account. The results show the substitution of the Cr3+ ion for an octahedral Fe3+ ion to be energetically favorable relative to its substitution for a tetrahedral Fe3+ one. It is also shown that the antisite defect, where the Cr3+ ion substitutes for Y3+ at a dodecahedral site with the expelled Y3+ ion substituting for an octahedral Fe3+ ion, is possible under certain processing conditions. For the Al3+ /Cr3+ co-doped Y3Fe5O12, the Al3+ and Cr3+ ions were found to, respectively, substitute for the tetrahedral and octahedral Fe3+ ions. The energy values obtained suggest this defect structure to be insensitive to the processing conditions and/or the presence of undetected impurities. The structural and magnetic implications of these defect structures are discusse