Ferrimagnetic nanostructures for magnetic memory bits

Increasing the magnetic data recording density requires reducing the size of the individual memory elements of a recording layer as well as employing magnetic materials with temperature-dependent functionalities. Therefore, it is predicted that the near future of magnetic data storage technology involves a combination of energy-assisted recording on nanometer-scale magnetic media. We present the potential of heat-assisted magnetic recording on a patterned sample; a ferrimagnetic alloy composed of a rare earth and a transition metal, DyCo$_5$, which is grown on a hexagonal-ordered nanohole array membrane. The magnetization of the antidot array sample is out-of-plane oriented at room temperature and rotates towards in-plane upon heating above its spin-reorientation temperature (T$_R$) of ~350 K, just above room temperature. Upon cooling back to room temperature (below T$_R$), we observe a well-defined and unexpected in-plane magnetic domain configuration modulating with ~45 nm. We discuss the underlying mechanisms giving rise to this behavior by comparing the magnetic properties of the patterned sample with the ones of its extended thin film counterpart. Our results pave the way for novel applications of ferrimagnetic antidot arrays of superior functionality in magnetic nano-devices near room temperature.Comment: 19 pages, 4 figure

Ordered La0.7Sr0.3MnO3 nanohole arrays fabricated on a nanoporous alumina template by pulsed laser ablation

Highly ordered nanohole arrays of [Formula: see text] manganite have been synthesized using pulsed laser deposition on nanoporous alumina template. Their structure and phase formation were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). The magnetic measurements were performed with respect to temperature and field and exhibit a ferromagnetic to paramagnetic transition at 284 K. In addition, the temperature dependence of electrical resistance was measured at different magnetic fields and an insulating phase throughout all the temperatures was observed. The low temperature ferromagnetic insulating state is discussed by the presence of a canted ferromagnetic state induced by the nanoholes. The present work shows the feasibility of combining both the nanoporous alumina template and pulsed laser ablation for the fabrication of perovskite manganite nanohole arrays which can also be extended to fabricate other multicomponent oxide nanohole materials.M K is thankful to FCT, Portugal for the Grant No. SFRH/ BPD/75110/2010. The authors acknowledged the financial supports from the projects NORTE-07–0124-FEDER000070, CERN/FIS-NUC/0004/2015 and IF/00686/2014

Magnetically active lithium-ion batteries towards battery performance improvement

Lithium-ion batteries (LIBs) are currently the fastest growing segment of the global battery market, and the preferred electrochemical energy storage system for portable applications. Magnetism is one of the forces that can be applied improve performance, since the application of magnetic fields influences electrochemical reactions through variation of electrolyte properties, mass transportation, electrode kinetics, and deposits morphology. This review provides a description of the magnetic forces present in electrochemical reactions and focuses on how those forces may be taken advantage of to influence the LIBs components (electrolyte, electrodes, and active materials), improving battery performance. The different ways that magnetic forces can interact with LIBs components are discussed, as well as their influence on the electrochemical behavior. The suitable control of these forces and interactions can lead to higher performance LIBs structures and to the development of innovative concepts.Work supported by the Portuguese Foundation for Science and Technology (FCT): projects UID/FIS/04650/2020, UID/CTM/50025/2020, UID/QUI/50006/2020, PTDC/FIS-MAC/28157/2017, Grant SFRH/BPD/112547/2015 (C.M.C.), and Investigator FCT Contract CEECIND/00833/2017 (R.G.) and 2020.04028.CEECIND (C.M.C.), as well POCH and European Union. Financial support from the Basque Government Industry and Education Departments under the ELKARTEK and PIBA (PIBA-2018-06) programs is also acknowledged

Ferrimagnetic DyCo5 nanostructures for bits in heat-assisted magnetic recording

Increasing the magnetic data recording density requires reducing the size of the individual memory elements of a recording layer as well as employing magnetic materials with temperature-dependent functionalities. Therefore, we predict that the near future of magnetic data storage technology involves a combination of energy-assisted recording on nanometer-scale magnetic media. We present the potential of heat-assisted magnetic recording on a patterned sample; a ferrimagnetic alloy composed of a rare-earth and a transition metal DyCo5, which is grown on a hexagonal-ordered nanohole array membrane. The magnetization of the antidot array sample is out-of-plane oriented at room temperature and rotates towards in plane upon heating above its magnetic anisotropy reorientation temperature (TR) of 350 K, just above room temperature. Upon cooling back to room temperature (below TR), we observe a well-defined and unexpected in-plane magnetic domain configuration modulating with 45 nm. We discuss the underlying mechanisms giving rise to this behavior by comparing the magnetic properties of the patterned sample with the ones of its extended thin-film counterpart. Our results pave the way for future applications of ferrimagnetic antidot arrays of superior functionality in magnetic nanodevices near room temperature

Micromagnetism of permalloy antidot arrays prepared from alumina templates

Magnetic hysteresis processes of hexagonal arrays of permalloy antidots have been studied by means of micromagnetic simulations as a function of geometrical parameters. The ideal system shows a maximum of the coercive field as a function of the antidot diameter. The simulated magnetic behavior has been compared with experimental values for antidot arrays of permalloy prepared from alumina templates with thicknesses between 2 and 60 nm, showing a monotonic increase of the coercive field as a function of the antidot diameter. We show that the introduction into simulations of the combination of variable antidot diameters from bottom to top due to the fabrication process and, more importantly, large geometrical domains, which break the sample symmetry, solves the discrepancy between the simulations and the experiment.This work was supported by the Spanish Ministerio de Economia y Competitividad under Projects MAT2010-20798-C05-01 and FIS2010-20979-C02-02

Magnetic antidot to dot crossover in Co and Py nanopatterned thin films

Under the terms of the Creative Commons Attribution License 3.0 (CC-BY).-- et al.The crossover from antidot to dot magnetic behavior on arrays patterned in a ferromagnetic thin film has been achieved by modifying only the geometry. A series of antidot arrays has been fabricated on cobalt with fixed diameter d and by reducing the period of the array p from pd to p<d. A dramatic change in the coercivity dependence with p, correlated with a significant modification in the magnetic domain structure observed by x-ray photoemission electron microscopy, evidences the crossover. An intermediate regime has been found between the superdomain structure present in antidot arrays and the array of astroid-state noncorrelated dots. The study has been reproduced for a different ferromagnetic material, permalloy, and supported by micromagnetic simulations. © 2014 American Physical Society.The financial support of MINECO-FEDER MAT2011/23791, MAT2012-38318-C03-03, MAT2012-36844, FIS2010-20979-C02-02, and Basque Government Project No. PI2012-47 is acknowledged.Peer Reviewe

Co nanostructures in ordered templates: comparative FORC analysis

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. © 2013 IOP Publishing Ltd.This work was performed under support by the Spanish Ministry of Economia y Competitividad, through project MAT2010-20798-C05-01. M P Proenca, D C Leitao and C T Sousa acknowledge FCT for grants SFRH/BPD/84948/2012, SFRH/BPD/72359/2010 and SFRH/BPD/82010/2011, respectively. K J Merazzo thanks the University of Costa Rica and CSIC for the financial support. L G Vivas thanks the International Iberian Nanotechnology Laboratory (INL) for a studentship. J Ventura acknowledges financial support through FSE/POPH. The authors acknowledge funding from FCT through the Associated Laboratory—IN.Peer Reviewe