Mössbauer studies of Y3Fe5 − xAlxO12 nanopowders prepared by mechanochemical method

Abstract

A series of Al substituted yttrium iron garnet (Al-YIG) nanopowders with nominal formula of Y 3 Fe 5−x Al x O 12 which x varied in steps of 0.0, 0.5, 1.0, 1.5 and 2.0 were prepared via mechanochemical processing. The samples were milled for 40 h in a high energy planetary mill and then calcined at different temperatures from 1,300 to 1,100 • C. X-ray diffraction patterns reveal that the structure of nanopowders are bcc and the garnet phase has been obtained after calcining. The average crystallite sizes are in the range of 24-45 nm, using Scherrer's formula. The lattice constant of the samples decreases by increasing Al concentration. To investigate the site preference of Al 3+ ions, room temperature 57 Fe Mössbauer spectra for the samples were recorded and analyzed. The hyperfine field values for octahedral and tetrahedral sites of the samples decrease by increasing x value. This decrease in magnetic hyperfine field reflects a reduction of the superexchange interaction by the progressive substitution of Al for Fe, which is also evident in the behavior of the magnetization and T C for the samples.

The Structural and the Magnetic Properties of Aluminum Substituted Yttrium Iron Garnet

“…In addition, RT Mössbauer spectra for the samples with 0 ≤ x ≤ 0.8 were fitted with three magnetic components, two corresponding to octahedral sites and one to tetrahedral sites 15 . On the other hand, Motlagh et al have shown that a systematic line broadening was observed in the Mössbauer spectra with the increase of Al 3+ concentration, which can be attributed to the presence of hyperfine field distribution because of the random distribution of Al 3+ in the octahedral and tetrahedral sites 16 .…”

“…Based on the previous studies, aluminum-substituted iron in YIG were synthesized by different methods such as sol-gel method 14,17,18 , co-precipitation method 19 , and ball milling 16 . Mössbauer spectra for synthesized garnets were fitted with different numbers of components corresponding to Fe 3+ in octahedral and tetrahedral sites.…”

Modification of the Magnetic Properties of Co₂Y Hexaferrites by Divalent and Trivalent Metal Substitutions

“…Finally, the hyperfine interactions in representative samples were investigated using 57 Fe Mössbauer spectroscopy (MS). This spectroscopy is based on the local Mössbauer effect [107], which was extensively used to investigate the local chemical environment, valence state, and site symmetry of Fe in alloys [108][109][110][111][112], intermetallic compounds [113][114][115], geological samples [116,117], garnets [118][119][120][121], and various types of ferrites [122][123][124][125]. Mössbauer spectra for the samples were collected over 512 channels using a conventional constant acceleration Mössbauer spectrometer operating with 57 Co/Cr source.…”

Microwave-hydrothermal synthesis of Y3Fe3.35Al1.65O12 nanoparticles for magneto-hyperthermia application

“…Above Curie temperature ferromagnetic material becomes paramagnetic. When exposed to an external magnetic field, YIG generates heat due to both Neel and Brown relaxation [15]. Once these particles reach Curie temperature, no heat is generated preventing overheating and damaging human tissues.…”

“…Once these particles reach Curie temperature, no heat is generated preventing overheating and damaging human tissues. The substitution of metal ions in the ferrite structure can affect the magnetic, electrical and dielectric properties of ferrites [15]. As Grasset et al demonstrated [16], aluminum substituted YIG (Y 3 Fe 5−x Al x O 12 , 0 ≤ x ≤ 2) decreases Curie point near body temperature by adjusting Fe/Al ratio, allowing such particles self-regulated and safe-guarded for hyperthermia applications.…”