Magnetism – Experimental group

Properties and applications of ferromagnetic nanostructures

Diego Bisero, Lucia Del Bianco, Federico Spizzo

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

Nanostructures: examples

1D2D 3D

Why nanostructures?

Ferromagnetic nanostructures

By Tem5psu, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=35116887

The size of domains and domain walls is comparable with that of the nanostructures

… size affects the properties ...

LThey are small ...

size/shape: new degrees of freedom to affect the magnetic properties

Research area: stripe magnetic domains D. Bisero

● 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

This kind of materials may be used as a sensor of mechanical stress or as an actuator

H

Rotatable magnetic anisotropy in thin films with stripe domains

Research area: nanomagnetic logic gates D. Bisero

- 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

Current technological paradigm: CMOS

From thermodinamical considerations, there is a minimal amount of energy required for erasing 1 bit of information:

kBT ln 2

Landauer Limit

Research area: nanomagnetic logic gates D. Bisero

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

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

D. BiseroExperimental methods: MFM and MOKE

Magnetic Force Microscope (MFM) Magneto Optical Kerr Effect (MOKE)

D. Bisero

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

Solid State Physics – Experimental magnetism groupstripe magnetic domain – nanomagnetic logic gates

master’s degree (LM) thesis

Research area: magnetic nanoparticles for biomedical applications F. Spizzo / L. Del Bianco

Diameter ~ 5 ÷ 10 nm

μ

The nanoparticle is just one magnetic domain

~ giant magnetic moment

magnetic nanoparticle

bio-functionalization layerIncreases the nanoparticles bio-compatibility and affects nanoparticles aggregation

✔ 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)

Research area: magnetic nanoparticles for biomedical applications F. Spizzo / L. Del Bianco

SPION: SuperParamagnetic Iron Oxide Nanoparticles

Magnetic analysis:

✔ aggregation state✔ relative concentration✔ mutual magnetic interactions✔ nanoparticles-covering interactions✔ nanoparticles-solvent interactions

Experimental methods: SQUID/Mössbauer F. Spizzo / L. Del Bianco

SQUID(superconductive quantum interference device)

Magnetic analysis:

✔ aggregation state✔ relative concentration✔ mutual magnetic interactions✔ nanoparticles-covering interactions✔ nanoparticles-solvent interactions

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Mössbauer spectroscopy (Fe)

Research area: magnetoplasmonic materials L. Del Bianco

Plasmonic resonance

Ligand moleculeDNA / 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.

Magnetoplasmonics: combination of plasmonic and magnetic properties

Research area: magnetoplasmonic materials L. Del Bianco

Magnetoplasmonic material: Au + Co

Growth method: co-sputtering

Au Co

substrate

Aims:● to produce thin films with a fine

intermixing of Au and Co (AuxCo1-x) [NEW!]

● to investigate the magnetic properties of the resulting material

● to use the same material to produce nanostructures for magnetoplasmonic applications

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In collaboration with Dep. of Physics and AstronomyUniversity of Padua

Experimental methods: magnetoplasmonic materials L. Del Bianco

Magnetoplasmonic material: Au + Co

Growth method: co-sputtering

Au Co

substrate

Aims:● to produce thin films with a fine

intermixing of Au and Co (AuxCo1-x)

● to investigate the magnetic properties of the resulting material

● to use the same material to produce nanostructures for magnetoplasmonic applications

SQUID

Magneto Optical Kerr Effect (MOKE)

F. Spizzo / L. Del Bianco

L. Del Bianco office 009 lucia.delbianco@unife.itF. 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

Solid State Physics – Experimental magnetism groupMagnetic nanoparticles for biomedical applications – magnetoplasmonic materials

Bachelor degree (LT) thesis - Master degree (LM) thesis

Research area: magnetic gas sensors B. Fabbri / F. Spizzo

Co: magnetostrictive ferromagnetmechanical stress magnetic properties

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electric field structural deformation

Research area: magnetic gas sensors B. Fabbri / F. Spizzo

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electric field structural deformation

Co: magnetostrictive ferromagnetmechanical stress magnetic properties

Research area: magnetic gas sensors B. Fabbri / F. Spizzo

F. Spizzo office 006 spizzo@fe.infn.itB. Fabbri office 110 barbara.fabbri@unife.it

Main collaborations:Elettra - Synchrotron light source - Trieste

Solid State PhysicsExperimental magnetism group & Sensors and Semiconductors group

magnetic gas sensors

Master degree (LM) thesis