A simple method for measuring intrinsic blocking temperature in superparamagnetic nanomaterials

• Main Authors: Bahmanrokh, Ghazaleh, Hashim, Mansor, Ismail, Ismayadi, Soltani, Nayereh, Vaziri, Parisa, Shafie, Mohd Shamsul Ezzad, Navasery, Manizheh
• Format: Article
• Language: English
• Published: Springer 2013
• Online Access: http://psasir.upm.edu.my/id/eprint/52282/1/A%20simple%20method%20for%20measuring%20intrinsic%20blocking%20temperature%20in%20superparamagnetic%20nanomaterials.pdf; http://psasir.upm.edu.my/id/eprint/52282/; http://rd.springer.com/article/10.1007/s10948-012-1742-7
• Institution: Universiti Putra Malaysia

Temperature-dependent magnetic flux density (B) data, clearly exhibiting a transition temperature called intrinsic blocking temperature for some metallic samples in zero field cooled-warmed (ZFC-W) curves without employing an external magnetic field, has been obtained by a simple method. The reasons of the increase and decrease in the measured B-field at low temperature in zero magnetic-field were discussed. Co, CoPt3 and Co/Au, CoPt 3/Au core-shell nanoparticles, prepared by the reverse-micelle microemulsion method, were used as test materials. The blocking temperature was measured at a cusp of the measured magnetic field, B (produced by the sample), versus the temperature curve during warming up of the sample from a very low temperature (≤15 K) to room temperature. All the samples showed a blocking temperature at 45, 50, 40, and 42 K, respectively, for Co, CoPt3, Co/Au, and CoPt3/Au nanoparticles. A completely intrinsic behavior of the sample's magnetic moment was revealed by our method since no applied external field was used, yielding a truly spontaneous magnetization behavior.