n. ponpandian – bu-nst 1 of xx bharathiar university coimbatore nanostructures and its...
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Bharathiar UniversityCoimbatore
Nanostructures and its Applications
N. Ponpandian
Department of Nanoscience and TechnologyBharathiar UniversityCoimbatore 641 046
Email: [email protected] Web: http://www.bunst.org
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ELECTRON WAVES Separate NanoSCIENCE from MicroSCIENCE
The discovery that electrons = waves led to QUANTUM MECHANICS
A weird, new, counter intuitive, non-Newtonian way of looking at the nano world
With a particular impact upon our understanding of electrons: Electrons => Waves
How do you figure out an electron’s wavelength?electron = h / p “De Broglie’s Relationship”
( = electron wavelength, h = Planck’s Constant, p = electron’s momentum)
This relationship was based on series of experiments late 1800’s / early 1900’s
To put the size of an electron’s wavelength in perspective:
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Quantum Mechanics
Planck’s Wavelength = h/p (or) h/mv
When mv >> h – Quantum effects are not observables
mv ~ h - Quantum effects are observable
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How to see the Nanoparticles?
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Bharathiar UniversityCoimbatoreSize of Things (red = man-made things)
Millimeters Microns Nanometers
Ball of a ball point pen 0.5Thickness of paper 0.1 100Human hair 0.02 - 0.2 20 – 200Talcum Powder 40Fiberglass fibers 10Carbon fiber 5 Human red blood cell 4 – 6E-coli bacterium 1Size of a modern transistor 0.25 250Size of Smallpox virus 0.2 – 0.3 200 – 300___________________________________________________________________________________________________
Electron wavelength: ~10 nm or less
Diameter of Carbon Nanotube 3Diameter of DNA spiral 2Diameter of C60 Buckyball 0.7Diameter of Benzene ring 0.28Size of one Atom ~0.1
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Bharathiar UniversityCoimbatoreSurface Area in Nanomaterials
A = 4 x 2 a x a + 2 a2 = 8 a2 + 2 a2 = 10 a2
A = 6 x a x a + 6 a x a = 12 a2
2a
a aa
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Bharathiar UniversityCoimbatoreSurface Area in Nanomaterials
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Surface Area in Nanomaterials
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Bharathiar UniversityCoimbatoreSurface Area in Nanomaterials
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Bharathiar UniversityCoimbatoreSurface Energy
Surface atoms posses more energy than bulk atoms
Consequently, surface atoms are more chemically reactive
Nanoparticles posses enhanced chemical reactivity
Example: NASA is exploring aluminum nanoparticles for rocket propulsion due to their explosiveness.
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Bharathiar UniversityCoimbatoreNanoparticle Catalysis
Macroscopic Gold is chemically inert.
Gold nanoparticles are used to catalyze chemical reactions.
Example: Reduced pollution in oxidation reactions (i.e., environmentally friendly
Nanoparticle Catalysis Research Group, Tsukuba, Japan
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Bharathiar UniversityCoimbatoreMacroscopic melting temperature
At macroscopic length scales, the melting temperature of materials in size-independent.
For example, an ice cube and a glacier both melt at the same temperature (32˚ F)
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Bharathiar UniversityCoimbatoreNanoscale melting temperature
Nanocrystal size decreases
Surface energy increases
Meling point decreases
Example: 3 nm CdSe nanocrystal melts at 700 K compared to bulk CdSe at 1678 K
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Bharathiar UniversityCoimbatoreOptical absorption
= hc/Eg
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Types of materials
1. Metals – No band gap2. Semiconductors – low band gap3. Insulators – very high band gap
What are Quantum dots?
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Bharathiar UniversityCoimbatoreWhat are Quantum dots?
• Quantum dots are nanocrystals of semiconductors that exhibit quantum confinement effects, once their dimensions get smaller than a characteristic length, called the Bohr’s radius.
• This Bohr’s radius is a specific property of an individual semiconductor
• Bohr’s radius can be equated with the electron–hole distance in an exciton that might be formed in the bulk semiconductor.
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Bharathiar UniversityCoimbatoreWhat is special in QDs
Valence band
Conduction band
towards nm
• Below this length scale (Bohr’s radius) the band gap (the gap between the electron occupied energy level, similar to HOMO, and the empty level, similar to LUMO), which are is size-dependent.
• Band gap is Size Dependent
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Structural differences
Bulk CarbonNanoscale Carbon
Carbon Nanotubes Sumio Iijima - 1991
C60 (Buckeyball)Smalley, Curl, Kroto
1996 Nobel Prize
Graphite Diamond
Mechanical Properties - CNT
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Bharathiar UniversityCoimbatoreWhat makes CNTs different from one another?
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Bharathiar UniversityCoimbatorePhysics of carbon nanotube
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Bharathiar UniversityCoimbatoreCNT – Field emission displays
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Bharathiar UniversityCoimbatoreFe filled MWCNT: Bio-compatible nanomagnets
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Bharathiar UniversityCoimbatoreFe filled MWCNT: Bio-compatible nanomagnets
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Bharathiar UniversityCoimbatore
Magnetism
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Bharathiar UniversityCoimbatoreAutomative Magnetics
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Bharathiar UniversityCoimbatoreA technology which impacts the environment !
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Bharathiar UniversityCoimbatoreHysteresis Loop
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Bharathiar UniversityCoimbatoreHysteresis Loop
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Ferromagnetic Domains
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Grain size > exchange lengthsoft magnetic properties as grain size
1
2
0 1
c cs
s
AKH p
J D
J Dp
i AK
1
2
0 1
c cs
s
AKH p
J D
J Dp
i AK
Grain size < exchange lengthsoft magnetic properties as grain size 2 3
4 60 1
1c c
s
sJ Ap
AKH p
J D
i K D
4 61
3
4 61
3
c cs
cs
K DH p
J A
K DH pc J A
Why nanocrystalline materials t of have excellent soft magnetic properties
? D
Lex
Random Anisotropy Model
Effect of nanosize on magnetic property
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Bharathiar UniversityCoimbatoreMagnetic properties of nanostructured materials
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Bharathiar UniversityCoimbatoreSuperparamagnetism
Response of superparamagnets to applied field described by Langevin model
Qualitatively similar to paramagnets
At room temperature superparamagnetic materials have a much greater magnetic susceptibility per atom than paramagnetic materials
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Biomedical Applications of Magnetic Nanoparticles
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Bharathiar UniversityCoimbatoreMagetism and medicine
• Iron and living things Many animals use magnetic fields to navigate Synthesize hemoglobin Role of iron in neurodegenerative disease
• Medical applications Removal of iron splinters, shrapnel, etc. Holding prosthetics Guiding instruments through the body MRI
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Bharathiar UniversityCoimbatoreBiomedical applications of magnetic nanoparticles
• Magnetic imaging
• Magnetic heating (Hyperthermia)
• Targeted drug delivery
• Detection/purification/isolation
• Manipulation
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Goal: Separate/detect/isolate one type of cell from others, often when the target is present in very small quantities
Magnetic Sorting
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Functionalized nanoparticles
R
Ligand
O
OO-O-
Magnetic Sorting, Detection
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Cells
Add to Samples
Magnetic Sorting
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Magnetic nanoparticles bond with targeted cells
Magnetic Sorting
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Retain desired cells by applying a magnetic field
Magnetic Sorting
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• Cancer cell growth is slowed or stopped at 42 °C - 46 °C
• Magnetic materials inside the body generate heat due to• Hysteresis• Brownian motion• Eddy currents
• Nanoparticles provide • uniform heating• non-invasive delivery• multiple treatments
• Human clinical trials in progress (Germany)
Hyperthermia
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Bharathiar UniversityCoimbatoreMagnetic Hyperthermia for Cancer Treatment
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Bharathiar UniversityCoimbatoreMagnetic resonance imaging
Non-invasive method used to render images of the inside of an object
Primarily used in medical imaging to demonstrate pathological or other physiological alterations of
living tissuesMRI is currently the most efficient imaging
procedure used in medicine
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Bharathiar UniversityCoimbatoreTypical MRI device
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Bharathiar UniversityCoimbatoreTypical MRI images
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Bharathiar UniversityCoimbatoreProblems in MRI
Low contrast between different tissuesLow contrast between a healthy tissue and tumors
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Bharathiar UniversityCoimbatoreContrast agents
Different contrast agents are administered in 40–50% of all MR examinations in order to improve the efficiency of this procedure
Contrast agents are diagnostic pharmaceutical compounds containing paramagnetic or superparamagnetic metal ions or nanoparticles that affect the MR-signal properties of surrounding tissues
Gadolinium chelates are the most widely used extracellular, non-specific contrast agents
Organ specific contrast agents include superparamagnetic iron oxides nanoparticles stabilized with appropriate biopolymers or biocompatible synthetic polymers
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Clinically approved superparamagnetic contrast agents stabilized with biopolymers
Ferumoxide (Endorem, Feridex) dextran stabilized
Ferumoxtran (Sinerem, Combidex) dextran stabilized
Ferucarbotranum (Resovist) carboxydextran stabilized
Used for intravenous applications
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Bharathiar UniversityCoimbatoreMRI of liver tumor
Normal liver tissue contains phagocytic Kupffer cells darkening after dextran-coated SPIO application
Cancer cells do not contain Kupffer cells after dextran-coated SPIO application tumor is brighter that surrounding tissue
Before SPIO application
After SPIO application
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Bharathiar UniversityCoimbatoreMRI of gastrointestinal tract
Small bowel before (left) and after (right) application of the oral contrast agent
Oral application of superparamagnetic nanoparticles
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Bharathiar UniversityCoimbatoreMRI of gastrointestinal tract
Commercially available contrast agents:
Ferumoxsil (GastroMARK, Lumirem) silicon-coated superparamagnetic iron
oxide
Ferristene (Abdoscan) sulphonated styrene-divinylbenzene latex particles (Ø 3.5 μm) with bound superparamagnetic
nanoparticles
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Nanomedicine
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Nanomedicine is an interdisciplinary field of science, even a simple project needs contributions from physicists, engineers, material chemists, biologists and end users, such as an orthopaedic surgeon.
A mature nanomedicine will require the ability to build structures and devices to atomic precision, hence molecular nanotechnology and molecular manufacturing are key enabling technologies for nanomedicine.
Medicine must catch up with the technology level of the human body before it can become really effective. The result will be the ability to analyse and repair the human body as completely as we can repair a conventional machine today.
If the nanoconcept holds together, it could be the groundwork for a new industrial revolution.
BUT: can all different scientists and engineers work together to achieve crossover dreams?
Nanomedicine : An Overview
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Bharathiar UniversityCoimbatoreHistory
Despite the importance of nanotechnology, literature review of robotics in 1993 included not a single reference to nanotechnology or nanomedicine.
The first nanomedical device design technical paper in 1998 by Freitas: Respirocyte – an Artificial Red Cell.
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Bharathiar UniversityCoimbatoreNanostructures in Nature
Nature has created nanostuctures for billenia. Biological systems are an existing proof of molecular nanotechnology.
Biology is an ingenious form of nanotechnology, even very simple living cells are able to duplicate. So far there is no machine of any size or type, which could do the same.
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Bharathiar UniversityCoimbatoreReplication
Replication is a basic capability for molecular manufacturing. Still some scientists think that medical nanorobots need not ever replicate.
It is unlikely that the FDA would ever approve a use of a medical nanodevice that was capable of in vivo replication. Replicators will be very tightly regulated by governments everywhere. In practice you would not want anything that could replicate itself to be turned loose inside your body.
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Bharathiar UniversityCoimbatoreNanodreams
Pollution-free industry will guarantee the well-being for the nature.
Nanomedicine will eliminate virtually all common diseases, all medical pain and suffering => theoretically eternal life.
Extension of human capabilities.
New era of peace. People who are well-fed, well-clothed, well-educated, healthy and happy will have little motivation to make war.
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Bharathiar UniversityCoimbatoreNanohorrors
Self replicating nanorobots could become massive chemical and biological weapons.
Changes to human properties, such as brains, respiration, muscles and DNA will be uncontrolled and may threat the existence of human being.
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Bharathiar UniversityCoimbatorePotential Applications of Nanomedicine
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Bharathiar UniversityCoimbatoreHuman Targets
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Bharathiar UniversityCoimbatoreDrug Delivery I
Nanoparticles can deliver drugs in a sophisticated ways, like target specific and trigger based drug dose. Target specific delivery enables
the use of lower doses, because the whole body is not saturated with the drug.
The side effects will be minimized, and it is possible to use stronger drugs, which could not be used by conventional drug delivery.
The use of gold particles in cancer healing is an example target specific action. Gold plated spheres are linked to
tumor cells. Nanoshells can be heated from the outside using an infrared source. Heating the shells destroy the cancerous cells, leaving the surrounding tissue unharmed.
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Bharathiar UniversityCoimbatoreImproved Imaging
Using magnetic nano particle can Improve imaging with better contrast agents and helps to diagnose diseases more sensitively.
The method enables the detection of very small tumors and other organisms which cause disease. When the diagnostics is improved the healing will also be easier.
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Bharathiar UniversityCoimbatoreDNA Analyses
Semiconductor nanocrystals, quantum dots, absorb only photons of light omitting just the right wavelength for their size.
Use of a variety of sizes and concentrations of quantum dots produces a spectral bar code with distinct spectral lines. Such method allows multiple labels.
Fast and accurate DNA testing, comparison of genetic material, rewriting DNA sequences in vivo, and even home DNA test systems.
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Bharathiar UniversityCoimbatoreNanobarcode® Technique I
SurroMed company is developing nanobarcode® technique with researchers from the Penn State University.
The idea is to use little metallic bars. Consecutively alternating gold- and silver-bands on a bar are interpreted as individual bits.
Twenty bands equal twenty bits ≈ 106 alternatives.
The bands can be interpreted with an optical microscope.
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Bharathiar UniversityCoimbatoreNanobarcode® Technique II
Numerous DNA-testers can be attached to a single bar, the testers combine with receptor molecules. The complex formation results a multiple DNA-sequence analysis. Also antibody molecules can be attached to a surface of a bar, after an immunologic reaction peptide hormones can be analysed.
Hundreds of components can be measured from one milliliter of serum, multiple test tubes and plentiful blood samples become unnecessary.
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Bharathiar UniversityCoimbatoreSuperior Implant Materials
The connection between implant material and bone/ surrounding tissues is a key factor to a successful and long-term use of prostheses.
Nano-scale modifications of implant surfaces would improve implant durability and biocompatibility.
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Bharathiar UniversityCoimbatoreCleaning Robots I
Teeth cleaning robots collect harmful bacteria from the mouth.
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Bharathiar UniversityCoimbatoreCleaning Robots II
Similar cleaning robots can be used in lungs. We have natural macrophages in alveoli, but they are not able to metabolize foreign particles like fibers of asbestos and toxic effects of smoking from the lungs.
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Bharathiar UniversityCoimbatoreCleaning Robots III
Extra fat can be removed from the arteries with cleaning robots.
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Bharathiar UniversityCoimbatoreRespirocyte
It is an artificial mechanical red blood cell floating along in the bloodstream. A spherical (d = 1 μm) nanomedical device is made of 18*109 atoms (mostly carbon).
The design of respirocyte was the first technical paper on nanomedical device design. It was published in 1998 by Robert A. Freitas.
It is important to notice that molecular nanotechnology violates no physical laws and there are technical paths leading to useful results.
Respirocyte device cannot be built today
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Bharathiar UniversityCoimbatoreImproving
Brains
A nanostructured data storage device measuring a volume about the size of a single human liver cell can store an amount of information equivalent to the entire library.
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Bharathiar UniversityCoimbatoreArtificial Tissues and Organs
Researchers hope to figure out ways to regenerate skin, bone and more sophisticated organs.
At present auto-, allo- and xenografts plus some artificial materials are being used for reconstruction of damaged tissues and organs.
The amount of auto- and allografts is limited, and allo- and xenografts carry a risk of infection (HIV or BSE).
So the need and interest for artificial regeneration definitely exists!
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Bharathiar UniversityCoimbatoreProperties of Medical Nanodevices
Shape and size
Biocompatibility
Powering Communicatio
n Navigation
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Magnetic Thin Films for
Modern Storage Devices
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The Nobel Prize in Physics 2007
for the discovery of Giant Magnetoresistance
Albert Fert
Université Paris-SudUnité Mixte de
Physique CNRS/THALES Orsay, France
Peter GrünbergForschungszentrum
Jülich Jülich, Germany
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The first step of spin electronics
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Magnetic Trilayers
A. Scherz, S. Sorg, M. Bernien, N. Ponpandian et. al. , Physical Review B 72 (2005) 054447
Trilayer is a prototype to study magnetic interlayer exchange coupling.
System Studied : Co/Cu/Ni/Cu(100)
Two trivial limits:
(i) dCu = 0 direct coupling (Ni-Co alloy)(ii) dCu = large no coupling (NiCo powder)
Objectives:
To study the interlayer exchange coupling effects between the magnetic layers as a function of the thickness of Cu and Ni layers
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FM1
FM2
Magnetic Trilayers in Current Technology
Ferromagnetic couplingResistance = low
Antiferromagnetic couplingResistance = high
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Why MRAM?
MRAM = Fast + Dense + Non-Volatile
SRAM
DRAM
Flash
MRAM combines
Silicon technology &
Magnetic thin film technology
To acheive
Fast, Dense, Non-Volatile
Solid state memory
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Effect of Interlayer Exchange Coupling
A. Scherz, S. Sorg, M. Bernien, N. Ponpandian et. al. , Physical Review B 72 (2005) 054447
XMCD probe the sign of Jinter
Excellent agreement between experiment and theory in TC shift
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Why Organic Molecules?
Switching in Fe-Porphyrin Miniaturization of information storage system
Organic semiconductors have been used to fabricate promising devices such as OLEDs, FETs and photovoltaic cells
Organic molecules contain only lighter elements and soo Spin – orbit coupling is minimalo transport of spin-polarized current over long
distances
Objectives:
To combine organic semiconductors with magnetic materials to develop novel devices such as MMRAM and MMSDs
o MMRAM – molecular magnetic random access memory
o MMSDs – molecular magnetic spin devices
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83 Nature Materials 6, 516-520 (2007)
Fe-Porphyrin Thermally and chemically stable Chemical properties can be
modified through synthesis with different ‘centre atom‘ and substituent groups
Present Study:
To asses the orientation of the Fe OEP molecules on the surfaces of ferromagnetic Ni (or) Co
type of magnetic ordering the magnetic orientation
Sytem Studied:
Fe-porphyrin/15ML Ni (or) 5 ML Co on Cu(100)
Fe-octaethylporphyrin chloride (Fe-OEP)
molecule
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Angular dependent NEXAFS
Orientation of Fe-Porphyrin
Nature Materials 6, 516-520 (2007)
Same fine structures (Co and Ni) Very similar absorption geometry Normal incidence - * resonance dominates Grazing incidence - * resonance dominates From N K–edge - molecules are intact with surfaces Plane of the four nitrogen atoms are aligned parallel to the
surafce
*
*
*
*
Corbon K-edge
Nitrogen K-edge
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Commercial Applications
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attentionQuestions Please !!!