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2018.06.12 cristina bran icmmcsic NanoFrontMag

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II Jornada científica NanoFrontMag - 12 de junio de 2018 - IMDEA Nanociencia
Cristina Bran
Grupo GMM-CSIC

Publicado en: Ciencias
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2018.06.12 cristina bran icmmcsic NanoFrontMag

  1. 1. Magnetization Ratchet in Cylindrical Nanowires Institute of Materials Science of Madrid, ICMM-CSIC C. Bran, J. A. Fernandez-Roldan, E. M. Palmero, E. Berganza, J. Meier, E. Calle, M. Jaafar, M. Foerster, L. Aballe, A. Fraile Rodriguez, A. Asenjo, R.P. del Real, O. Chubykalo-Fesenko and M.Vazquez cristina.bran@icmm.csic.es
  2. 2. 2D Magnetic nanowires => nanostrips M. Kläui et al., Phys. Rev. Lett. 95, 026601 (2005) DWs designed by: geometry, material.. DWs controlled by magnetic fields and electrical currents B. Borie et al., Phys. Rev. Appl. 8, 044004 (2017) A. Pushp et al. Nature Physics 9, 505(2013). J.H. Franken at al., Nature Nanotechnology 7, 499 (2012) cristina.bran@icmm.csic.es - Pinning by notches in Py strips - Specific chirality DWs follow specific paths as function of chirality DWs manipulated by rotating magnetic fields DWs energy engineered to favor a unidirectional ratchet-like propagation
  3. 3. 3D cylindrical nanowires N. Biziere et al, Nano Lett. 13, 2053(2013) S. Da-Col et al., Phys. Rev. B 89, 180405(2014) TDWBPDW D. Reyes et al, Nano Lett. 16, 1230(2016) cristina.bran@icmm.csic.es A. Fernandez-Pacheco et al., Scientific Reports 3, 1492 (2013) NWs in alumina membranes NW growth by FEBID Advantages: Tailored DWs Stability High velocities Easy and cheap to fabricate NW shadow C. Bran et al. Phys. Rev. B 96, 125415 (2017)
  4. 4. 3D cylindrical nanowires z y x Transverse Domain Wall mz -1 0 1 H Vortex (Bloch Point) Domain Wall Tail-to-tail Head-to-head DWs determined by geometry and material cristina.bran@icmm.csic.es
  5. 5. Domain Wall (DW) manipulation Full control over DW is required for information storage technologies, logic systems and sensors. Magnetic Racetrack Memory Stuart Parkin. Science 320 (2008) Magnetic Logic Circuit D. Allwood et al. Science 309 (2005) MOTIVATION DWs Well defined Full control Evaluate the possibility to control DWs by means of a diameter- modulated geometry and tailored anisotropy. Objetive cristina.bran@icmm.csic.es
  6. 6. • Anodic Aluminum Oxide (AAO) template • Mild and Hard Anodization (HA)+pulses • rapid growth • ordered pores with D=20-200 nm 0 1000 2000 3000 4000 -20 0 20 40 60 80 100 120 140 160 0 1000 2000 3000 4000 0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 I(mA) time (s) 0 30 60 90 120 150 V(V) Voltage(V) Time (s) Type A 0 2000 4000 6000 8000 -20 0 20 40 60 80 100 120 140 160 2000 3000 4000 5000 6000 7000 8000 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 I(mA) time (s) -20 0 20 40 60 80 100 120 140 V(V) (C) (B) Voltage(V) Time (s) (A) Type B or C Synthesis and preparation cristina.bran@icmm.csic.es
  7. 7. Type A: D=20-250nm, L1>20um Type B: D1=130nm, D2=140nm, L1=4-800nm L2=<50nm Type C: D1=130nm, D2=100nm, L1=200-1000nm L2=200-500nm Synthesis and preparation cristina.bran@icmm.csic.es
  8. 8. 30 nm Cu30 nm Cu FeCo=300-900 nm 30 nm Cu Multisegmented nanowires FMNM cristina.bran@icmm.csic.es
  9. 9. C. Bran et al, ACS Nano 2018 DOI: 10.1021/acsnano.8b02153 MOKE measurements -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 Long.Kerr(normalized) 360 Oe 260 Oe 195 Oe -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 Long.Kerr(normalized) 275 Oe 363 Oe 260 Oe -400 -200 0 200 400 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 Long.Kerr(normalized) H (Oe) 365 Oe 265 Oe Multisegmented nanowires cristina.bran@icmm.csic.es
  10. 10. XMCD-PEEM measurements NW shadow DW M NW shadow Magnetic field Multisegmented nanowires
  11. 11. XMCD-PEEM measurements (in remanence) XAS Unidirectional Ratchet–like DW propagation H Multisegmented nanowires cristina.bran@icmm.csic.es C. Bran et al, ACS Nano 2018 DOI: 10.1021/acsnano.8b02153
  12. 12. XMCD-PEEM measurements (in remanence) XAS Multisegmented nanowires -900 -600 -300 0 300 600 900 -1.0 -0.5 0.0 0.5 1.0 M/Ms Applied field (Oe) H cristina.bran@icmm.csic.es C. Bran et al, ACS Nano 2018 DOI: 10.1021/acsnano.8b02153
  13. 13. H Simulations: J.A. Fernandez-Roldan and O. Chubykalo-Fesenko Multisegmented nanowires 200 250 300 350 400 450 500 550 30 Msat = 2.00 T; Aex = 25.0e-12 J/m Kc1 = 1.0e4 const. J/m3 grainsize := 5.0e-9 ; UNITS: nm. Length: 3210 Diameter: 80 FeCo Cu PARAMETERS (FeCo) cristina.bran@icmm.csic.es J. A. Fernandez-Roldan, R. Perez del Real, C. Bran, M. Vazquez and O. Chubykalo-Fesenko, Nanoscale, 2018 A.Vansteenkiste et al.,The design and verification of mumax3, AIP Advances 4, 107133 (2014).
  14. 14. -1200 -600 0 600 1200 -1,0 -0,5 0,0 0,5 1,0 -510 -425 -340 -1 0 1 m(a.u) H(Oe) m(a.u.) H(Oe) b c d e e) H = - 460 Oe L R c) H = - 425 Oe L R b) H = - 360 Oe x y z z y bc d e L R d) H = - 445 Oe Pinned a 1 0 -1 mx a) H = 0 Oe x y z z y H
  15. 15. 15 Total and internal magnetic energies in the NW as function of the longitudinal magnetization The configurations b-d are dynamical and do not correspond to true minima of the total energy In real experimental those configurations may be stabilized by the presence of defects. Multisegmented nanowires-Micromagnetic simulations cristina.bran@icmm.csic.es
  16. 16.  Unidirectional and step-like propagation  The reversal is often pinned at specific locations associated with Cu layers  The reversal process starts in the shortest segment  Micromagnetic simulations->complex process: sequential switching, formation of vortices and skyrmion tube states  Remagnetization ratchet is induced by the variable length of the segments J. A. Fernandez-Roldan, R. Perez del Real, C. Bran, M. Vazquez and O. Chubykalo-Fesenko, Nanoscale, 2018 C. Bran et al. ACS Nano 2018 cristina.bran@icmm.csic.es XMCD-PEEM capable to determine the magnetization distribution at the surface and inside the NW Conclusions

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