Abstract
Synthesis of the polycrystalline Ba2-xSrxNi2(Fe1-yAly)12O22 (x = 0.0, 1.5, y = 0.00, 0.01, and 0.03) was accomplished by employing the polymerizable complex method. The samples were investigated for the crystallographic and magnetic properties by x-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Mössbauer spectrometer. Based on the results of the refined XRD patterns, all samples were confirmed to have a rhombohedral structure with space group R-3m. Moreover, six distinguished sublattices were identified, which were four octahedral sites (18hVI, 3bVI, 6cVI, and 3aVI) and two tetrahedral sites (6cIV*, 6cIV). The lattice constant of a0 and c0 decrease via Sr, Al substitution because the ionic radius of Sr2+ (1.12 Å) is smaller than that of Ba2+ (1.34 Å), and the ionic radius of Al3+ (0.535 Å) is smaller than that of Fe3+ (0.645 Å). The zero-field-cooled (ZFC) measurement was applied at 100 Oe between 4.2 and 295 K and it revealed the spin transition temperature (TS). Substitution of Sr ions increased TS. Al ions were further substituted after the substitution of Sr ions, and TS increased above room temperature. The Mössbauer spectra fit six distinguish sublattices: 18hVI, 3bVI, 6cIV, 6cIV*, 6cVI, and 3aVI. The isomer shift of all samples indicated that the charge state of Fe ions is Fe3+. The Mössbauer spectra obtained with respect to temperature change confirmed the changes in the magnetic hyperfine field curves at Ts.
Highlights
The Y-type hexaferrite has certain physical characteristics, such as the magnetoelectric (ME) effect based on spin-current model, multiferroicity, spin structure according to temperature and magnetic field
We investigated the magnetic properties by substituting Sr ions and small amounts of Al ions for Ba2Ni2Fe12O22
The lattice constants of a0, c0 and unit cell volume were decreased by substituting the Sr ion from Ba2Ni2Fe12O22 (x=0.0, y=0.00)
Summary
The Y-type hexaferrite has certain physical characteristics, such as the magnetoelectric (ME) effect based on spin-current model, multiferroicity, spin structure according to temperature and magnetic field. The ME effects are observed based on strong super-exchange interactions between Fe ions.. Some Y-type hexaferrites show a magnetoelectric effect near room temperature such as Ba2Mg2Fe12O22, Ba0.5Sr1.5Zn2(Fe1-xAlx)12O22.10,11 It has been reported that the helimagnetic structure is stabilized by partially substituting Ba ions with Sr ions.. In Ba0.5Sr1.5Co2Fe12O22, the helical magnetic structure was observed at 255 K and higher than the 215 K observed in Ba2Co2Fe12O22.4,13 The magnetic properties changed due to the super-exchange interaction from ionic radius difference of Ba ions and Sr ions.. Non-magnetic Al ion doping results in a change in TS and Curie temperature by reducing the spin moment per unit cell and adjusting the spin exchange strength.
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