Co nanostructures in ordered templates: comparative FORC analysis

Abstract

A comparative study on the structural and magnetic properties of highly ordered hexagonal arrays of Co nanoholes, nanowires, nanopillars and nanotubes, with tuned pore/wire/tube diameters, is here presented. The magnetic interactions and their dependence on the geometric features of the arrays were studied using first-order reversal curves (FORCs). For all nanostructures we observe an increase of the magnetostatic interactions with the templates' pore diameter, with the higher (smaller) values found for the nanowire (nanohole) arrays. For the smallest diameters studied (35 nm), all types of arrays could be considered as almost isolated nanostructures, where local interactions prevail. In particular, both nanotube and nanohole arrays exhibit considerable local magnetostatic interactions coming from the stray fields within each void or empty core. On the other hand, the coercivity is found to decrease with diameter for the elongated nanostructures, while it increases with the pore diameter for the nanohole arrays. This behavior is associated with the magnetization reversal mechanisms present in each array. This work highlights a versatile route to tailor the size, geometrical arrangement and magnetostatic interactions of ordered arrays and demonstrates their importance for the tuning of the magnetic behavior of nanometric devices.

Large-Pore Mesoporous Ho3Fe5O12 Thin Films with a Strong Room-Temperature Perpendicular Magnetic Anisotropy by Sol–Gel Processing

“…They are constantly undergoing changes to adapt to modern device requirements and, in recent years particularly, magnetic nanostructures have been in the focus of interest, with much attention paid to size and orientation effects. [1][2][3] Many routes to achieving nanoscale materials with different morphologies, including wires, particles, and thin films, to mention only a few, have been reported in the literature. [4][5][6] Among them are solution-processing routes such as solvothermal and sol-gel methods, physical deposition techniques, mechanochemical approaches, and others.…”

Electrochemical synthesis and magnetism of magnetic nanotubes

“…Figure 24.16 shows that when comparing NW and NT arrays with outer diameters of around 40 nm and center-to-center distances of around 105 nm, higher values of H k c and S k are found for the NW arrays, which can be attributed to their higher shape anisotropy factor (Proenca et al, 2012b(Proenca et al, , 2013c. The study of the coercivity and squareness through the hysteresis loops provides valuable information on the magnetization reversal mechanisms and the magnetic interactions between the nanoelements of the array.…”

“…) is to measure major magnetic hysteresis loops. This technique has proved to be particularly efficient and powerful in the study of highly interacting systems, such as magnetic NPs (Pike et al, 1999;Brem et al, 2006;Lavin et al, 2012;Ursachi et al, 2011), thin film nanohole arrays (Beron et al, 2011;Merazzo et al, 2011;Proenca et al, 2013c), and FM NWs (Rotaru et al, 2011;Spinu et al, 2004;Beron et al, 2008;Salem et al, 2013;Dobrota and Stancu, 2013;Vivas et al, 2012b). To obtain the local magnetostatic properties, using the same experimental setup for simplicity, Mayergoyz (1985) proposed the analysis of multiple minor hysteresis loops, called first-order reversal curves (FORCs).…”

Template Assisted Deposition of Ferromagnetic Nanostructures: from Antidot Thin Films to Multisegmented Nanowires

“…The development by Masuda and Fukuda of the two step anodization process for the fabrication of highly ordered nanoporous anodic aluminum oxide (AAO) templates [4] paved the way for the template-assisted deposition of a wide variety of nanomaterials. These nanomaterial families range from nanowire [5,6] and nanotube arrays [7] nanoparticle clusters [8] and antidot thin films [9,10], among others. The highly self-ordered hexagonal symmetry of the pores arrangement exhibited by the AAO templates displays narrow pore size distributions having well-defined interpore distances.…”