High temperature structural and magnetic properties of cobalt nanorods

Atmane, Kahina Aït; Zighem, F.; Soumare, Yaghoub; Ibrahim, Mahmoud; Boubekri, Rym; Maurer, Thomas; Margueritat, Jérémie; Piquemal, Jean‐Yves; Ott, F.; Chaboussant, Grégory; Schoenstein, Frédéric; Jouini, N.; Viau, Guillaume

doi:10.1016/j.jssc.2012.08.009

Cited by 46 publications

(44 citation statements)

References 33 publications

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“…Figure 1b shows 3 hysteresis loops for the same structure calculated by the macro spin, μmag and oHmag method. The results are in good agreement with experimental data [1].…”

Section: Packed Nanorodssupporting

confidence: 90%

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Modelling of Packed Co Nanorods for Hard Magnetic Applications

Toson

Wallisch

Asali

et al. 2014

EPJ Web of Conferences

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Abstract. We present a numerical algorithm based on the bullet physics library to generate densely packed (39% -41%) structures of high-aspect-ratio nanorods for finite element micromagnetic simulations. The coercivities μ 0 H c of the corresponding Cobalt nanorod structures vary between 0.50T and 0.67T, depending on the overall orientation of nanorods, which is in good agreement with experimental results. The simulations make it possible to estimate the coercivity loss due to incoherent reversal processes (27%) as well as the gain due to shape anisotropy (59%). Our calculations show permanent magnets consisting of packed Co nanorods with an energy density product (BH) max of 83kJ/m³. We estimate that this value can be increased to 103kJ/m³ by increasing the packing density from 40% to 45%. Another way to optimize (BH) max is the usage of novel materials. By varying the anisotropy constant K 1 and the saturation polarisation J S we found lower limits for these parameters to reach a certain energy density product. To increase (BH) max to 160 kJ/m³, K 1 and J S have to be in the order of 450kJ/m³ and 2.25T, respectively. The thermal stability of this approach was verified by elastic band calculations. Cobalt nanorods with a diameter of 10nm and a height of 50nm are thermally stable at room temperature, but problematic at 900K. Doubling the nanorods' height to 100nm increases that limit considerably.

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“…Figure 1b shows 3 hysteresis loops for the same structure calculated by the macro spin, μmag and oHmag method. The results are in good agreement with experimental data [1].…”

Section: Packed Nanorodssupporting

confidence: 90%

“…A densely packed structure of high-aspect-ratio (1:5 -1:10) cobalt nanorods exploits both sources of anisotropy and experiments showed that these structures maintain high coercivity values at high temperatures, because the shape anisotropy is temperature-independent [1].…”

Section: Introductionmentioning

confidence: 99%

Modelling of Packed Co Nanorods for Hard Magnetic Applications

Toson

Wallisch

Asali

et al. 2014

EPJ Web of Conferences

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“…Due to the absence of defects and to their mono--crystalline state, experimental coercivity can reach values larger than 0.5 T at room temperature. We showed in previous work that half of the observed coercivity could be accounted for by the magneto--crystalline anisotropy (Maurer 2007 andAit--Atmane 2013). The remaining part can be attributed to the shape anisotropy contribution.…”

Section: Introductionmentioning

confidence: 75%

Optimization of the magnetic properties of aligned Co nanowires/polymer composites for the fabrication of permanent magnets

et al. 2014

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We aim at combining high coercivity magnetic nanowires in a polymer matrix in a view to fabricate rare--earth free bonded magnets. In particular, our aim is to fabricate anisotropic materials by aligning the wires in the polymer matrix. We have explored the different parameters of the fabrication process in order to produce a material with the best possible magnetic properties. We show that the choice of a proper solvent allows obtaining stable nanowire suspensions. The length and the type of the polymer chains play also an important role. Smaller chains (M w <10000) provide better magnetization results. The magnetic field applied during the casting of the material plays also a role and should be of the order of a fraction of a tesla. The local order of the nanowires in the matrix has been characterized by TEM and Small Angle Neutron Scattering. The correlation between the local order of the wires and the magnetic properties is discussed. Materials with coercivity µ 0 H c up to 0.70 T at room temperature have been obtained.2

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“…The first term is expected to be temperature dependent while the second is almost constant as function of temperature (in the range 20-200 K) and only differs for different morphologies (author?) [32]. The effective anisotropy acting then on a single nanowire can be written as the sum of the magnetocrystalline and shape contributions if both are aligned with the length of the nanowire.…”

Section: Nanowire Shape and Length Effectsmentioning

confidence: 99%

Morphology control of the magnetization reversal mechanism in Co80Ni20 nanomagnets

Mercone

Zighem

Léridon

et al. 2015

Journal of Applied Physics

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Nanowires with very different size, shape, morphology and crystal symmetry can give rise to a wide ensemble of magnetic behaviors whose optimization determines their applications in nanomagnets. We present here an experimental work on the shape and morphological dependence of the magnetization reversal mechanism in weakly interacting Co80Ni20 hexagonal-close-packed nanowires. Non-agglomerated nanowires (with length L and diameter d) with a controlled shape going from quasi perfect cylinders to diabolos, have been studied inside their polyol solution in order to avoid any oxidation process. The coercive field HC was found to follow a standard behavior and to be optimized for an aspect ratio L d > 15. Interestingly, an unexpected behavior was observed as function of the head morphology leading to the strange situation where a diabolo shaped nanowire is a better nanomagnet than a cylinder. This paradoxical behavior can be ascribed to the growth-competition between the aspect ratio L d and the head morphology ratio d D (D being the head width). Our experimental results clearly show the importance of the independent parameter (t = head thickness) that needs to be considered in addition to the shape aspect ratio ( L d ) in order to fully describe the nanomagnets magnetic behavior. Micromagnetic simulations well support the experimental results and bring important insights for future optimization of the nanomagnets morphology.

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High temperature structural and magnetic properties of cobalt nanorods

Cited by 46 publications

References 33 publications

Modelling of Packed Co Nanorods for Hard Magnetic Applications

Modelling of Packed Co Nanorods for Hard Magnetic Applications

Optimization of the magnetic properties of aligned Co nanowires/polymer composites for the fabrication of permanent magnets

Morphology control of the magnetization reversal mechanism in Co80Ni20 nanomagnets

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