The Magnetic Properties of Fe/Cu Multilayered Nanowires: The Role of the Number of Fe Layers and Their Thickness

Abstract

Multi-segmented bilayered Fe/Cu nanowires have been fabricated through the electrodeposition in porous anodic alumina membranes. We have assessed, with the support of micromagnetic simulations, the dependence of fabricated nanostructures’ magnetic properties either on the number of Fe/Cu bilayers or on the length of the magnetic layers, by fixing both the nonmagnetic segment length and the wire diameter. The magnetic reversal, in the segmented Fe nanowires (NWs) with a 300 nm length, occurs through the nucleation and propagation of a vortex domain wall (V-DW) from the extremities of each segment. By increasing the number of bilayers, the coercive field progressively increases due to the small magnetostatic coupling between Fe segments, but the coercivity found in an Fe continuous nanowire is not reached, since the interactions between layers is limited by the Cu separation. On the other hand, Fe segments 30 nm in length have exhibited a vortex configuration, with around 60% of the magnetization pointing parallel to the wires' long axis, which is equivalent to an isolated Fe nanodisc. By increasing the Fe segment length, a magnetic reversal occurred through the nucleation and propagation of a V-DW from the extremities of each segment, similar to what happens in a long cylindrical Fe nanowire. The particular case of the Fe/Cu bilayered nanowires with Fe segments 20 nm in length revealed a magnetization oriented in opposite directions, forming a synthetic antiferromagnetic system with coercivity and remanence values close to zero.

Interwire and Intrawire Magnetostatic Interactions in Fe‐Au Barcode Nanowires with Alternating Ferromagnetically Strong and Weak Segments

“…The above allows us to make a direct comparison of a pair of samples, such as Fe(100)/Au(30) and Fe(200)/Au(30), because the number of cycles has been recognized as a more critical factor affecting the possible magnetostatic interactions than the total length in the barcode system. [ 24,25 ]…”

“…The above allows us to make a direct comparison of a pair of samples, such as Fe(100)/Au (30) and Fe(200)/Au (30), because the number of cycles has been recognized as a more critical factor affecting the possible magnetostatic interactions than the total length in the barcode system. [24,25] We monitored the composition-dependent morphological changes of the BNW arrays embedded in the nanoporous AAO template using fractures of the samples. We observed the sharp borders between the Fe and Au segments (Figures 1 (a)-(h)).…”

Electrodeposited Magnetic Nanowires with Radial Modulation of Composition

“…Nanowires (NWs) are among the most studied curvilinear systems [ 12 , 13 , 14 ]. In these systems, changes of composition along the axial direction, i.e., synthesizing multilayers along the growth direction, can be used to tune the magnetic properties [ 15 , 16 ] or to stabilize topologically complex domain structures [ 17 , 18 ]. By appropriately choosing the thickness of consecutive multilayers, a magnetization ratchet in the magnetization dynamics can also be produced [ 19 ].…”