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Salaheldeen M, Nafady A, Abu-Dief AM, Díaz Crespo R, Fernández-García MP, Andrés JP, López Antón R, Blanco JA, Álvarez-Alonso P. Enhancement of Exchange Bias and Perpendicular Magnetic Anisotropy in CoO/Co Multilayer Thin Films by Tuning the Alumina Template Nanohole Size. NANOMATERIALS 2022; 12:nano12152544. [PMID: 35893512 PMCID: PMC9332129 DOI: 10.3390/nano12152544] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Revised: 07/14/2022] [Accepted: 07/21/2022] [Indexed: 02/04/2023]
Abstract
The interest in magnetic nanostructures exhibiting perpendicular magnetic anisotropy and exchange bias (EB) effect has increased in recent years owing to their applications in a new generation of spintronic devices that combine several functionalities. We present a nanofabrication process used to induce a significant out-of-plane component of the magnetic easy axis and EB. In this study, 30 nm thick CoO/Co multilayers were deposited on nanostructured alumina templates with a broad range of pore diameters, 34 nm ≤ Dp ≤ 96 nm, maintaining the hexagonal lattice parameter at 107 nm. Increase of the exchange bias field (HEB) and the coercivity (HC) (12 times and 27 times, respectively) was observed in the nanostructured films compared to the non-patterned film. The marked dependence of HEB and HC with antidot hole diameters pinpoints an in-plane to out-of-plane changeover of the magnetic anisotropy at a nanohole diameter of ∼75 nm. Micromagnetic simulation shows the existence of antiferromagnetic layers that generate an exceptional magnetic configuration around the holes, named as antivortex-state. This configuration induces extra high-energy superdomain walls for edge-to-edge distance >27 nm and high-energy stripe magnetic domains below 27 nm, which could play an important role in the change of the magnetic easy axis towards the perpendicular direction.
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Affiliation(s)
- Mohamed Salaheldeen
- Physics Department, Faculty of Science, Sohag University, Sohag 82524, Egypt
- Departamento de Física, Universidad de Oviedo, C/Federico García Lorca 18, 33007 Oviedo, Spain; (R.D.C.); (M.P.F.-G.); (J.A.B.)
- Departamento de Física Aplicada, EIG, Universidad del País Vasco, UPV/EHU, 20018 San Sebastián, Spain
- Correspondence: (M.S.); (P.Á.-A.)
| | - Ayman Nafady
- Chemistry Department, College of Science, King Saud University, Riyadh 11451, Saudi Arabia;
| | - Ahmed M. Abu-Dief
- Chemistry Department, Faculty of Science, Sohag University, Sohag 82524, Egypt;
| | - Rosario Díaz Crespo
- Departamento de Física, Universidad de Oviedo, C/Federico García Lorca 18, 33007 Oviedo, Spain; (R.D.C.); (M.P.F.-G.); (J.A.B.)
| | - María Paz Fernández-García
- Departamento de Física, Universidad de Oviedo, C/Federico García Lorca 18, 33007 Oviedo, Spain; (R.D.C.); (M.P.F.-G.); (J.A.B.)
| | - Juan Pedro Andrés
- Instituto Regional de Investigación Científica Aplicada (IRICA), Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain; (J.P.A.); (R.L.A.)
- Departamento de Física Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
| | - Ricardo López Antón
- Instituto Regional de Investigación Científica Aplicada (IRICA), Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain; (J.P.A.); (R.L.A.)
- Departamento de Física Aplicada, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
| | - Jesús A. Blanco
- Departamento de Física, Universidad de Oviedo, C/Federico García Lorca 18, 33007 Oviedo, Spain; (R.D.C.); (M.P.F.-G.); (J.A.B.)
| | - Pablo Álvarez-Alonso
- Departamento de Física, Universidad de Oviedo, C/Federico García Lorca 18, 33007 Oviedo, Spain; (R.D.C.); (M.P.F.-G.); (J.A.B.)
- Instituto Universitario de Tecnología Industrial de Asturias, Universidad de Oviedo, 33203 Gijón, Spain
- Correspondence: (M.S.); (P.Á.-A.)
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