New review article

Cylindrical nanowire arrays: From advanced fabrication to static and microwave magnetic properties”

Manuel Vazquez

Journal of Magnetism and Magnetic Materials 543 (2022) 168634

DOI: doi.org/10.1016/j.jmmm.2021.168634

This article reviews information on arrays of cylindrical magnetic nanowires grown electrochemically inside ordered nanoporous alumina membranes, summarizing some of the most relevant aspects about the advanced synthesis and their static and microwave magnetic properties. It details electrochemical synthesis of templates and of metallic nanowires either as single element (i.e., Fe, Ni, Co), alloys (i.e., CoFe, CoNi, FeNi) or modulated in composition (i.e., Ferromagnetic/Metal). Static and dynamic magnetic properties are overviewed, where magnetization easy axis can be switched from the nanowire direction to the template’s plane as the nanowire filling factor increases or at a compensation temperature, deriving from the energetic balance of anisotropy and magnetostatic interactions among nanowires. The perspectives of applications making use of microwave properties are also discussed.

This review article is written as homage to Prof. Sergio Rezende from Brazil. The data were mainly performed in our GNMP to which so many investigators have contributed along the last 20 years. Particular acknowledgement to Dr. Cristina Bran, responsible of the electrochemistry laboratory and nanowires research for the last 10 years, to Dr. Hernandez-Velez, Dr. Kleber Pirota and Dr. David Navas who set up the laboratory, to staff colleagues, Dr. Agustina Asenjo, Dr. Rafael Perez del Real and Dr. Oksana Chubykalo-Fesenko, and to many researchers contributing in PhD, as visiting scientists and international collaborators. It was supported by the Spanish MINECO, Project PID2019-108075RBC31, and the Regional Government of Madrid, Project S2018/NMT-4321 NANOMAGCOST-CM

New article

Narrow Segment Driven Multistep Magnetization Reversal Process in Sharp Diameter Modulated Fe67Co33 Nanowires”

 

Javier García, Jose A. Fernández-Roldán, Roque González, Miguel Méndez, Cristina Bran, Víctor Vega, Silvia González, Manuel Vázquez and Víctor M. Prida

 

Nanomaterials 11 (2021) 3077.

DOI: doi.org/10.3390/nano11113077

An interesting pathway to affect the dynamics of the magnetization reversal in magnetic nanostructures is to introduce geometrical modulations to act as nucleation or pinning centers for the domain walls. Considering the case of 3D magnetic nanowires, the modulation of the diameter across their length produce such effect as long as the segment diameter transition is sharp enough. Here, diameter modulated Fe67Co33 ferromagnetic nanowires were grown into prepatterned diameter modulated nanopores of anodized Al2O3 membranes. Morphological and compositional characterization was carried out by electron-based microscopy, while their magnetic behavior was measured on both individual bisegmented nanowires and their arrays. The magnetic hysteresis loops, as well as First Order Reversal Curve diagrams, point out that the magnetization reversal is carried out in two steps interpreted by micromagnetic modeling, where a shell of the wide segment reverses magnetization first, followed by the reversal of its core together with the narrow segment of the nanowire at once.

This research in collaboration with the University of Oviedo was funded by Spanish Ministerio de Ciencia e Innovación (MICINN) and Research Agency State (AEI), under grants number PID2019-108075RBC31 and PID2019-108075RBC32, and by the Regional Government of Madrid under the project S2018/NMT-4321

NANOMAGCOST-CM

New article

“Controlling devitrification in the FeSiB system without alloying additions”

X. Zhang, R. Perez del Real, M. Vazquez, W. Liang, J. Mesa, A. Jimenez and L.H. Lewis

Journal of Non-Crystalline Solids 576 (2022) 121277

DOI: doi.org/10.1016/j.jnoncrysol.2021.121277

Efficient electric machines require soft magnetic materials with superior properties. Here, significant differences in the primary devitrification process and the resulting microstructure of amorphous metallic Fe79Si11B10 alloys synthesized by two rapid solidification methods are confirmed: melt-spun ribbons and water-quenched microwires, investigated with calorimetric, structural, and magnetic probes. The primary devitrification process of ribbons occurs at higher temperature (by 80 K) with a faster exothermic heat release than that of quenched microwires, despite their common chemical composition and fully devitrified structural state. Primary devitrification reveals that ribbons exhibit a ~70% higher effective activation energy and ~110% larger value of Avrami exponent, indicating different devitrification routes taken by these two types of material. Ribbons crystallize via a continuous nucleation process partly relying on pre-existing surface nuclei, with an interface-controlled growth mechanism. In contrast, the quenched microwires devitrify solely from pre-existing nuclei, with diffusion-controlled growth. Differences are attributed to unique quenched-in structures created by the specific rapid solidification conditions. These results suggest approaches to control the microstructure in FeSiB compositions without the need for non-magnetic alloying additions.

This research has been funded in part by Northeastern University (Boston, USA), Fulbright España, the IEEE Magnetics Society Educational Seed Funding, and the Regional Government of Madrid under project S2018/NMT-4321 NanomagCOST-CM

New article

“Nanoimprinted and Anodized Templates for Large-Scale and Low-Cost Nanopatterning”

David Navas, David G. Trabada and Manuel Vázquez

Nanomaterials 11 (2021) 3430.

DOI: doi.org/10.3390/nano11123430

This work reports on an easy route for nanopatterning making use of ordered porous templates with geometries ranging from straight lines to square, triangular or rhombohedral lattices, for the designed growth of sputtered materials with engineered properties. The procedure is based on large-scale nanoimprinting using patterned low-cost commercial disks, as 1-D grating stamps, followed by a single electrochemical process that allows one to obtain 1-D ordered porous anodic templates. Multiple imprinting steps at different angles enable more complex 2-D patterned templates. Subsequent sputtering facilitates the growth of ferromagnetic antidote thin films (e.g., Co thin layers) with designed symmetries. This technique constitutes a non-expensive method for massive mold production and pattern generation avoiding standard lithographical techniques. It also overcomes current challenges of the two-stage electrochemical porous templates: (i) allowing the patterning of large areas with high ordering and/or complex antidot geometries, and (ii) being less-time consuming.

This work derives from the PhD thesis of David Gonzalez Trabada developed in our GNMP group

New Technological Project

“Microhilos Magnéticos para Sensores Magnetoelásticos”

A contract of Technological Support has been signed with the Universidad Pública de Navarra (Prof. J.I. Pérez de Landazábal) concerning the development of magnetic microwires as sensing elements for magnetoelastic sensors (2021). The project is supervised by M. Vazquez.

New technological project

Magnetic Microwire Research Project

A contract has been signed with the company Bartington Instrument Ltd., United Kingdom, to develop technologically advanced magnetic microwires (2021-2022). The project is supervised by M. Vazquez and R.P del Real.

New patent

“Magnetic microwires for energy-transporting biomedical applications”

US Patent Application Pub.No. US 2021/0101016 A1; Northeastern University, Boston and CSIC

Inventors: L.H. Lewis, R. P. del Real, M. Vazquez Villalabeitia and A.N. Koppes

Methods and devices including amorphous magnetic microwires are provided for biomedical energy transfer for diagnosis or therapy, to promote cellular growth, or to deliver pharmaceutical agents. Applications of the technology include sensors, actuators and therapeutic coatings and for increasing the amount, directionally, or length of nerve growth. The technology can also be utilized for nerve regeneration, hyperthermic treatment of tumors, vascular theranostics, probing and stimulating a nerve, sensing a biological condition, catheterization and micro-actuation.

This patent application is the result of a continuous collaboration of our GNMP group with the Northeastern University of Boston.

New article

“Evidence of Skyrmion-Tube Mediated Magnetization Reversal in Modulated Nanowires”

E. Berganza, J. Marqués-Marchán, C. Bran, M. Vazquez, A. Asenjo and M. Jaafar

 Materials 14 (2021) 5671

DOI://doi.org/10.3390/ma14195671

Magnetic nanowires, as individual building blocks for spintronic devices, constitute a well-suited model to design and study magnetization reversal processes, or to tackle fundamental questions, as the presence of topologically protected magnetization textures under particular conditions. Recently, a skyrmion-tube mediated magnetization reversal process was theoretically reported in diameter modulated cylindrical nanowires where a vortex nucleates at the end of the segments with larger diameter and propagates, resulting in a first switching of the nanowire core magnetization at small fields. Here, we show experimental evidence of the so-called Bloch skyrmion-tubes, using advanced Magnetic Force Microscopy modes to image the magnetization reversal process of FeCoCu diameter modulated nanowires. By monitoring the magnetic state during applied field sweeping, a detected drop of magnetic signal at a given critical field unveils the presence of a skyrmion-tube, due to mutually compensating stray field components.

This study is a collaboration between our GNMP group and the Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Germany and the Departamento de Física de la Materia Condensada and Condensed Matter Physics Center (IFIMAC), and the Instituto Nicolás Cabrera, at the Universidad Autónoma de Madrid.

New article

“Stochastic vs. deterministic magnetic coding in designed cylindrical nanowires for 3D magnetic networks”

C. Bran, E. Saugar, J.A. Fernandez-Roldan, R.P. del Real, A. Asenjo, L. Aballe, M. Foerster, A. Fraile Rodríguez, E.M. Palmero, M. Vazquez and O. Chubykalo-Fesenko

Nanoscale 13 (2021) 12587

DOI: 10.1039/d1nr02337c

 

Advances in cylindrical nanowires for 3D information technologies profit from intrinsic curvature that introduces significant differences with regards to planar systems. A model is proposed to control the stochastic and deterministic coding of remanent 3D complex vortex configurations in designed multilayered (magnetic/non-magnetic) cylindrical nanowires. This concept, introduced by micromagnetic simulations, is experimentally confirmed by magnetic imaging in FeCo/Cu multilayered nanowires. The control over the random/deterministic vortex states configurations is achieved by a suitable geometrical interface tilting of almost non-interacting FeCo segments with respect to the nanowire axis, together with the relative orientation of the perpendicular magnetic field. The proper design of the segments’ geometry (e.g. tilting) in cylindrical nanowires opens multiple opportunities for advanced nanotechnologies in 3D magnetic networks.

This work has been performed in collaboration between our GNMP group at ICMM/CSIC with ALBA Synchrotron Light Facility, CELLS, Barcelona, the Departament de Física de la Matèria Condensada, Universitat de Barcelona and the Group of Permanent Magnets and Applications, IMDEA Nanoscience, Madrid. It has been supported by the Spanish Ministry of Science and Innovation under Projects MAT2016-76824-C3-1-R, PID2019-108075RB-C31/AEI /10.13039/501100011033 and PGC2018-097789-B-I00 and the Regional Government of Madrid under Project S2018/NMT-4321 NANOMAGCOST-CM.

New Review Article

“Matteucci Effect and Single Domain Wall Propagation in Bistable Microwire under Applied Torsion”

 A. Jiménez, E. Calle, J.A. Fernandez-Roldan, R.P. del Real, R. Varga and M. Vázquez

Phys. Status Solidi A 2021, 2100284  

DOI: 10.1002/pssa.202100284

Systematic experimental results on the Matteucci effect in torsioned magnetostrictive FeSiB microwire are introduced observed during the propagation of a single domain wall (DW) under the action of axial driving magnetic field, Hdr. The Matteucci electromotive force (emf) is associated with depinning and annihilation of the DW. The emf amplitude is proportional to the DW velocity and the time derivative of the azimuthal magnetization, tailored by applied torsion. The clockwise/counterclockwise applied torsion dependence of Matteucci emf and DW velocity are experimentally determined for parallel and antiparallel Hdr. Asymmetric behaviors are observed for both, the sense of applied torsion and the direction of Hdr. The experimental data are discussed in terms of the magnetoelastic anisotropy introduced by torsion. Through analysis of the DW dynamics, such asymmetric behaviors are interpreted as a magnetochiral effect derived from the change of chirality of the propagating wall.

This Review Article is included in the special issue to celebrate the 60th anniversary of Physica Status Solidi, and it is a collaboration between our GNMP group and the Centre of Progressive Materials, P.J. Safarik University Kosiçe, Slovakia. It was supported by the Regional Government of Madrid under project S2018/NMT-4321 NANOMAGCOST-CM.