Thermally activated processes and superparamagnetism in Bi12MnO20 nanoparticles: A comparative study

JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS

卷:401

Article

de Oliveira, L. A. S.¹  Penton-Madrigal, A.²  Guimaraes, A. P.³  Sinnecker, J. P.³ 

[1] Univ Fed Rio de Janeiro, NUMPEX Nucleo Multidisciplinar Pesquisas, BR-25245390 Duque De Caxias, RJ, Brazil

[2] Univ La Habana, Fac Fis, Havana 10400, Cuba

[3] Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, RJ, Brazil

关键词: Fine-particle systems;    Temperature-hysteresis effect;    Relaxation effect;   

DOI  :  10.1016/j.jmmm.2015.11.013

来源: Elsevier

【 摘 要 】

Manganese sillenite (Bi12MnO20) nanoparticles having average particle size between 22 and 43 nm were synthesized by a low temperature soft chemical route under refluxing conditions. A careful structural and microstructural characterization by means of high resolution X-ray diffraction experiments and transmission electron microscopy is presented. The as-cast powder displayed an isotropic superparamagnetic (SPM) behavior with a blocked state for temperatures below TB 13.0 K. We used three different measurement techniques to extract and compare the Bi12MnO20 blocking temperatures. First, we extracted TB with the modified Bean-Livingstone model from the coercive field temperature dependence obtained from hysteresis curves measured as a function of temperature. Then, the blocking temperature distribution function, f (T-B), was obtained by deriving the zero field-cooled/field-cooled curves difference. For each applied field, the maximum of the distribution function gave us the mean blocking temperature value. Finally, the maximum of the magnetic susceptibility imaginary part as a function of frequency was used, combined with the Neel-Brown equation, to extract the blocking temperature. All measurement techniques yield an equivalent dependence of TB with H of the Bi12MnO20 superparamagnetic nanoparticles. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

Free