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Title: Effect on Physical, Electrical and Magnetic Properties of Strontium Hexaferrite Nanomaterial Doped with Binary Mixtures of Various Metal Ions
Authors: Ashiq, Muhammad Naeem
Keywords: Natural Sciences
Chemistry & allied sciences
Physical chemistry
Techniques, equipment & materials
Analytical chemistry
Inorganic chemistry
Organic Chemistry
Issue Date: 2009
Publisher: Quaid-i-Azam University Islamabad, Pakistan
Abstract: Five series of strontium hexaferrite nanomaterials with nominal compositions, SrZrxNixFe12-2xO19, SrZrxCuxFe12-2xO19, SrZrxMnxFe12-2xO19, SrZrxZnxFe12-2xO19 and SrZrxAlxGaxFe12-2xO19 (where x = 0.0-0.8) have been synthesized by the chemical co- precipitation method. The structural analysis is carried out by thermogravimetry (TG/DTG), powder X-ray diffraction (XRD) and energy dispersive X-ray fluorescence (ED-XRF) techniques. The DC electrical resistivity (ρ), dielectric constant (έ) and dielectric loss (tanδ) are measured by a two-point probe method and inductance capacitance resistance (LCR) meter, respectively. The magnetic susceptibility (χ) is measured by a magnetic susceptometer and the hysteresis loops, the saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) has been determined by the induction method. Thermal analysis reveals that the magnetoplumbite phase begins to form at a temperature of 873 K and is completed at 1193 K which is also complimented by the XRD studies. The average crystallites sizes of the samples of the five series are in the range of 26-62 nm. All the samples consist of pure single phase as confirmed by the magnetic susceptibility and XRD analysis. The nominal theoretical compositions of the samples are experimentally confirmed by the ED-XRF analysis. Except Zr-Mn substituted series all the samples show metal to semiconductor transition (TM-S). The drift mobility (μd) and activation energy (Ea) are calculated from the electrical resistivity data. The observed variation of electrical resistivity is explained on the basis of the electrons hopping between ferric and ferrous ions. The room temperature electrical resistivity and activation energy are increased by doping with Zr-Ni, Zr-Cu, Zr-Mn and Al-Ga series up to specific concentration but decreases continuously by substitution of Zr-Zn. The dielectric constant (έ) and dielectric loss (tanδ) are calculated in the frequency range of 100 Hz -1MHz and both the parameters decrease with increase in frequency. This behavior is explained on the basis of the Maxwell- Wagner and Koop’s models. The dielectric constant, dielectric loss and drift mobility increase with the increase in the dopant (Zr-Ni, Zr-Cu, Zr-Mn and Al-Ga) contents but increase by the substitution of Zr-Zn. The Curie temperature (Tc) is determined from the temperature dependence of magnetic susceptibility (χ) at temperature from 300 to 800 K. the value of Tc decreases for all the five series investigated here. The saturation magnetization (Ms) increases for Zr-M series (where M = Ni, Cu, Mn and Zn) but decreases for the Al-Ga series. The coercivity (Hc) decreases for all the present series. The variation of saturation magnetization,remanence (Mr) and coercivity with substituent concentration is explained on the basis of occupation of the substituted cations at different hexagonal sites. The increase in saturation magnetization, electrical resistivity and decrease in coercivity, dielectric constant, dielectric loss and drift mobility suggest that the Sr-hexaferrites doped with Zr-Ni, Zr-Cu and Zr-Mn are suitable for applications in high density recording media as well as in microwave devices but the Zr-Zn and Al-Ga substituted samples are more suitable for high density recording media and microwave devices, respectively.
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