Properties and applications of ferromagnetic nanostructures

Transcription

1 Properties and applications of ferromagnetic nanostructures Diego Bisero, Lucia Del Bianco, Federico Spizzo Magnetism Experimental group

2 Outline 1.Nanostructures: some examples 2.Why ferromagnetic nanostructures? 3.Research activity: stripe magnetic domains nanomagnetic logic gates magnetic nanoparticles for biomedical applications magnetoplasmonic materials magnetic gas sensors

3 Nanostructures: examples 1D 2D 3D Why nanostructures?

4 Ferromagnetic nanostructures They are small... L size affects the properties... The size of domains and domain walls is comparable with that of the nanostructures By Tem5psu, CC BY-SA 4.0, size/shape: new degrees of freedom to affect the magnetic properties

5 Research area: stripe magnetic domains D. Bisero Rotatable magnetic anisotropy in thin films with stripe domains Formation of stripe domains in thin magnetostrictive films with perpendicular magnetic anisotropy (FeGa, TbFeGa) Rotation of stripe domains by a magnetic field perpendicular to the stripe axis H This kind of materials may be used as a sensor of mechanical stress or as an actuator

6 Research area: nanomagnetic logic gates D. Bisero Current technological paradigm: CMOS - Based on silicon transistors - The information is binary (0 and 1 states) and associated to different values of the Voltage - Changing the state of a bit requires the flow of an electric current Heat generation From thermodinamical considerations, there is a minimal amount of energy required for erasing 1 bit of information: k B T ln 2 Landauer Limit

7 Research area: nanomagnetic logic gates D. Bisero Trying to reach the Landauer limit: NanoMagnetic Logic (NML) The information contained in one dot should be transferred coherently over the longest possible distance: Nanodot WIRES NML-based circuits process information by manipulating the magnetization states of single domain nanomagnets coupled to their nearest neighbors through magnetic dipole interactions. The state variable is the magnetization direction and computations can take place without the passage of an electric current

8 Experimental methods: MFM and MOKE D. Bisero Magnetic Force Microscope (MFM) Magneto Optical Kerr Effect (MOKE)

9 D. Bisero Solid State Physics Experimental magnetism group stripe magnetic domain nanomagnetic logic gates master s degree (LM) thesis D. Bisero office 008 bisero@fe.infn.it Main collaborations: University of Notre Dame, Notre Dame, Indiana, USA (Center for Nano Science and Technology) University Pierre and Marie Curie, Paris Universidad Complutense, Madrid University of Perugia

10 Research area: magnetic nanoparticles for biomedical applications F. Spizzo / L. Del Bianco magnetic nanoparticle μ bio-functionalization layer Increases the nanoparticles bio-compatibility and affects nanoparticles aggregation Diameter ~ 5 10 nm The nanoparticle is just one magnetic domain ~ giant magnetic moment manipulated thanks to a magnetic field low toxicity high specific surface If an external AC magnetic field is applied, magnetic nanoparticles may release heat to the tissues (hyperthermia)

11 Research area: magnetic nanoparticles for biomedical applications F. Spizzo / L. Del Bianco Magnetic analysis: aggregation state relative concentration mutual magnetic interactions nanoparticles-covering interactions nanoparticles-solvent interactions SPION: SuperParamagnetic Iron Oxide Nanoparticles

12 Experimental methods: SQUID/Mössbauer F. Spizzo / L. Del Bianco SQUID (superconductive quantum interference device) energy By Joël Gubler - Own work, CC0, /index.php?curid= rel. transmission source I=3/2 I=1/2 δ 0 velocity / mm/s isomer shift quadrupole splitting when Vzz > 0 rel. transmission absorber δ ΔEQ Δ mi ± 3/2 ± 1/2 ± 1/2 0 velocity / mm/s Magnetic analysis: aggregation state relative concentration mutual magnetic interactions nanoparticles-covering interactions nanoparticles-solvent interactions Mössbauer spectroscopy (Fe)

13 Research area: magnetoplasmonic materials L. Del Bianco Ligand molecule DNA / protein When DNA/protein interact with the ligand molecule, he refractive index of the medium surrounding the nanoparticles changes; due to that, a shift in the position of the absorption maximum is observed. Plasmonic resonance Magnetoplasmonics: combination of plasmonic and magnetic properties

14 Research area: magnetoplasmonic materials L. Del Bianco Magnetoplasmonic material: Au + Co 1 2 Growth method: co-sputtering Au Co 3 Au 4 substrate Aims: to produce thin films with a fine intermixing of Au and Co (Au x Co 1-x ) [NEW!] to investigate the magnetic properties of the resulting material to use the same material to produce nanostructures for magnetoplasmonic applications 200 nm In collaboration with Dep. of Physics and Astronomy University of Padua

15 Experimental methods: magnetoplasmonic materials L. Del Bianco Magnetoplasmonic material: Au + Co Growth method: co-sputtering Au Co SQUID substrate Aims: to produce thin films with a fine intermixing of Au and Co (Au x Co 1-x ) to investigate the magnetic properties of the resulting material to use the same material to produce nanostructures for magnetoplasmonic applications Magneto Optical Kerr Effect (MOKE)

16 F. Spizzo / L. Del Bianco Solid State Physics Experimental magnetism group Magnetic nanoparticles for biomedical applications magnetoplasmonic materials Bachelor degree (LT) thesis - Master degree (LM) thesis L. Del Bianco office 009 lucia.delbianco@unife.it F. Spizzo office 006 spizzo@fe.infn.it Main collaborations: Department of Physics and Astronomy, University of Padua Department of Industrial Engineering, University of Padua Department of Molecular Biotechnology and Health Sciences, University of Turin ICMATE-CNR, Padua University of Perugia

17 Research area: magnetic gas sensors B. Fabbri / F. Spizzo O 2 1 CO 2 CO 2 ZnO: piezoelectric semiconductor electric field structural deformation O - e - e - O - Co: magnetostrictive ferromagnet mechanical stress magnetic properties

18 Research area: magnetic gas sensors B. Fabbri / F. Spizzo O 2 1 CO 2 CO 2 ZnO: piezoelectric semiconductor electric field structural deformation O - e - e - O - Co: magnetostrictive ferromagnet mechanical stress magnetic properties

19 Research area: magnetic gas sensors B. Fabbri / F. Spizzo Solid State Physics Experimental magnetism group & Sensors and Semiconductors group magnetic gas sensors Master degree (LM) thesis F. Spizzo office 006 spizzo@fe.infn.it B. Fabbri office 110 barbara.fabbri@unife.it Main collaborations: Elettra - Synchrotron light source - Trieste