9-13 July 2012
Africa/Johannesburg timezone
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An investigation of the structural and magnetic properties of Ho substituted BiFeO<sub>3</sub>

11 Jul 2012, 10:55
Oral Presentation Track A - Division for Condensed Matter Physics and Materials DCMPM1


Mr Mehluli Ncube (University of the Witswatersrand)

Abstract content <br> &nbsp; (Max 300 words)

The doping of BiFeO3 with lanthanide elements like Ho, with a radius smaller than Bi, is ideal to improve the ferroelectric and magnetic properties of BiFeO3, which in principle can cause structural distortions of the lattice that can enhance the electrical and magnetic [1] properties. In this paper, we report on the temperature dependence of the structural and magnetic properties of Ho substituted BiFeO3 (BHFO) which has been investigated by Mössbauer spectroscopy and X-ray diffraction (XRD). Mössbauer measurements were performed in-situ (300 – 748 K) on the as-synthesized BHFO sample.
The Mössbauer spectra were characterized by broadened features and the magnetic hyperfine splitting patterns, which are indicative of magnetic ordering mostly probably screwed or slightly antiferromagnetic ordering. The room temperature spectrum was fitted with two superimposed symmetric sextets, with similar hyperfine magnetic fields of Bhf1 = 50.1 T, and Bhf2 = 49.8 T in the Fe3+ state corresponding to rhombohedral BiFeO3 (BFO) as observed by De Sitter et al. [2], a Lorentzian doublet which is attributed to the paramagnetic impurity phase Bi25FeO40 and a singlet which is a result of the minority Bi2Fe4O9 impurity phase. The hyperfine fields of the sextet components decreased systematically with increasing temperature to a field distribution just below the Neel temperature. At temperatures, T > 588 K, the phase transitions are dominant and are attributed to the instability of BFO at such temperatures with weak reflections from the decomposition to the Bi25FeO40 and the Bi2Fe4O9 impurity phases [3]. An average Debye temperature, D = 240  81 K has been determined for BHFO using the from the temperature dependence of spectral area fractions which is lower than that cited for BiFeO3 [4].

[1] Al-Haj M., Cryst. Res. Technol., 45, 89–93, 2010.
[2] De Sitter J., Dauwe C., De Grave E., and Govaert A., Solid State Comm., vol. 18, pp. 645-646, 1976.
[3] Rancourt D. G. and Ping J. Y., Nuclear Instruments and Methods in Physics Research, vol. B58, pp. 85-97, 1991.
[4] Blaauw C. and Van der Woude F., J. Phy. C: Solid State Phy., vol. 6, pp. 1422-1431, 1973.

Main supervisor (name and email)<br>and his / her institution

Dr. Deena Naidoo
University of the Witwatersrand

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Primary author

Mr Mehluli Ncube (University of the Witswatersrand)


Prof. Dave Billing (University of the Witswatersrand) Dr Deena Naidoo (University of the Witswatersrand) Dr Diptiranjan Sahu (University of the Witswatersrand) Mr Hilary Masenda (University of the Witswatersrand) Prof. Krish Bharuth-Ram (University of KwaZulu Natal)

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