Angular-dependent magnetic properties of chemically synthesized single crystalline Co nanowires

Abstract

Angular-dependent measurements of magnetic properties could point the way for understating reversal modes of anisotropic nanoobjects for use in next generation of more powerful and permanent information storage devices. However, such measurements have been significantly less considered for chemically synthesized nanowires. Here, single crystalline hexagonal close-packed Co nanowires with an average length and diameter of 220 and 12 nm, respectively, are synthesized using a solvothermal method in a non-polar solvent. The angular-dependent (0° ≤θ ≤ 90°) magnetic properties are carefully studied by hysteresis loop measurements and first-order reversal curve (FORC) analysis after aligning the Co nanowires oriented along [001] direction in epoxy. While randomly oriented Co nanowires have a coercivity (H_c) and squareness (S_q) of 4.3 kOe and 0.54, respectively, they show enhanced magnetic properties (H_c = 7.9 kOe and S_q = 0.78) after alignment at θ = 0°. The FORC analysis indicates the formation of by-products such as nanoparticles and low aspect ratio nanorods in the synthesis of the Co nanowires, which are confirmed by high-resolution transmission electron microscopy. The variation of coercive field distribution (

) as a function of θ is studied, demonstrating a continuous increase in () for θ > 45°. This indicates that the aligned Co nanowires with high crystallinity may reverse their magnetization through a domain wall mode, being in accordance with the literature on the magnetization reversal mechanism taking place in electrochemically fabricated Co nanowire arrays.