Localized magnetization reversal processes in cobalt nanorods with different aspect ratios  

作　　者：Marc Pousthomis Evangelia Anagnostopoulou Ioannis Panagiotopoulos Rym Boubekri Weiqing Fang Frederic Ott Kahina Ait Atmane Jean-Yves Piquemal Lise-Marie Lacroix Guillaume Viau 

机构地区：[1]Universite de Toulouse, LPCNO, UMR 5215 INSA CNRS UPS, 135 av de Rangueil, 31077 Toulouse Cedex 4, France [2]Laboratoire Leon Brillouin, CEA/CNRS UMR 12, IRAMIS, CEA-Saclay, 91191 Gifsur Yvette, France [3]Department of Materials Science and Engineering, University ofloannina, Ioannina 45110, Greece [4]Universite Paris Diderot, Sorbonne Paris Cite ITODYS, CNRS UMR 7086, 15 rueJ.-A, de Baif, 75205 Paris Cedex 13, France

出　　处：《Nano Research》2015年第7期2231-2241,共11页纳米研究（英文版）

摘　　要：We present results of the synthesis of cobalt nanorods using the polyol process and the mechanism of magnetization reversal. We show that the nucleation step is significantly dependent on the nature of the ruthenium chloride used as the nucleating agent. This allows varying the diameter and aspect ratio of the cobalt nanorods independently. Co nanorods with aspect ratio, mean diameter, and mean length in the ranges ARm =3-16, Din= 7-25 nm, and Lm=30-300 nm, respectively, were produced using this method. X-ray diffraction and electron microscopy showed that a strong discrepancy between the structural coherence and morphological aspect ratio can exist because of stacking faults. The coercivity of assemblies of different nanorods was systematically measured, and the highest values were obtained for the smallest diameter and the largest structural coherence length. Micromagnetic simulations were performed to account for the dependence of the coercive field on the diameter. An important observation is that simple coherent magnetization rotation models do not apply to these magnetic nano-objects. Even for very small diameters （Dm = 5-10 nm） well below the theoretical coherent diameter Dcoh（CO）= 24 nm, we observed inhomogeneous reversal modes dominated by nucleation at the rod edges or at structural defects such as stacking faults. We conclude that, in order to produce high-coercivity materials based on nanowires, moderate aspect ratios of 5-10 are sufficient for providing a structural coherence similar to the morphological aspect ratio. Thus, the first priority should be to avoid the formation of stacking faults within the Co nanowires.

关 键 词：nanorod NANOWIRE PERMANENT MAGNETS MICROMAGNETIC calculations shape anisoteopy 

分 类 号：O[理学]