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Nano-Events | Nano Bugle

Category Archives: Nano-Events

Researchers at IBM make the smallest magnetic bit (next seminar at the INL)

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Researchers at IBM San Jose have just reported the  experimental demonstration of a magnetic bit made with only 12 atoms (press release).  Sebastian Loth, the first author of the paper, just published in Science  (link to the paper), will visit INL next week and give a seminar on Tuesday 31 January.

Non-volatile storage of digital  information, as recorded in conventional hard-disks, makes use of the  spin orientation of magnetic grains made of more than one million atoms.  The magnetic grains are made of ferromagnetic materials, so that  the  magnetic moment of each atom tends to point parallel to their neighbors,   in the so called ferromagnetic coupling, adding up to form a net  magnetization.  Magnetic grains have a so called easy axis, so that the  collective magnetization points either parallel or anti-parallel  to the  easy axis. These two possible stable orientations define the two  logical states of a classical bit, 0 or 1.

Increasing the storage density  in magnetic recording involves reducing the size of the magnetic grains,  which leads to a number of practical challenges involving the detection  of their magnetization and the loss of stability: the time scale for  unwanted flip of the magnetization  decreases exponentially  as the  volume of the particle is reduced.  This naturally leads to the question  of how small can the magnetic particle be which leads a  sufficiently  large lifetime for the spin orientation.

The experiment of the IBM team  addresses this question but changes the strategy in terms of the type of  magnetic material.  Instead of using  ferromagnetic nanoparticle they  use an  atomically engineered antiferromagnetic system, in which the  magnetic moments of a given atom likes to point anti-parallel to their  neighbors.  Taking advantage of a Scanning Tunneling Microscope (STM) they can move atoms, one by one, deposited on a surface, and design  structures with arbitrary shapes. In this instance they have fabricated  chains of a few (6,8) iron atoms, on top of a copper surface capped with  a single monolayer of an insulating material, Copper Nitride.

The antiferromagnetic coupling  between iron atoms  result in a vanishing total magnetization for a  given chain, which goes completely against the usual approach.  They can  get away with it taking advantage of a readout technique with atomic  scale resolution: the spin polarized scanning tunneling microscope (STM).    By reading the spin orientation of every atom in a given chain  , the IBM team has been able to  observe how the short chains of 4   atoms and less behave as quantum antiferroamgnets: the spin every atom  is in  a quantum superposition of being up and down, which results in an  average null magnetization for each atom, and the impossibility of  using such system so store digital information.

Interestingly, for chains of 6  atoms and higher the chains behave as expected in classical  antiferromagnets and have two stable orientations:  1) Even atoms up,  odd atoms down and 2) Even atoms down, odd atoms up.  Taking advantage  of the atomic scale readout  the IBM team could  trace the thermal  stability of the different chains and found how the stability improved  for larger chains.   In particular,  2 chains with 6 atoms lying  parallel, referred to as (2×6) have been shown to be suitable to store a  bit of classical information.

In addition to the use of STM to  fabricate the chains and to read their magnetization, the IBM team has  also shown how to write the logical state in a bit using electrical  pulses send with the STM.   Combining the 3  capabilities together, the   IBM group has fabricated a byte made with 8 (2×6) chains and has  recorded on it the digital code for the letters S, P, I and N.

Whereas there is a long way  between these experimental breakthroughs and massive commercial  applications, mostly duet  the low temperature and ultra-high vacuum   experimental conditions at which the experiments have been done,  the  IBM team has made it real the vision of  Feynman, back in 1959, in his  inspiring talkThere is Plenty of Room at the bottom” where he prophetically said  “When we get to the very, very small world – say circuits of seven atoms  – we have a lot of new things that would happen that represent  completely new opportunities for design”.   The  group of Theory of  Nanostructures at INL is making progress to understand the  working  principles of all these striking experiments.

Joaquín Fernández-Rossier, Staff Researcher at INL

Nanotechnology and Nanomedicine course at the INL (Braga, 17 – 21 October 2011)

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The International Iberian Nanotechnology Laboratory is organizing a Nanotechnology and Nanomedicine Course that will take place at INL from the 17th to the 21st of October 2011. The course provides an introduction to the scientific basis of nanotechnology, including changes in the properties of materials at the nanoscale, and the potential of nanotechnology and its application to biomedical sciences.

Click HERE to download the updated course program

It is a multidisciplinary course designed for PhD students (Physics, Chemistry, Biology, Pharmacy, Medicine, etc.) who are starting out in Nanomedicine.

Nanotechnology is a broad scientific field that involves the creation and use of materials and devices at the level of molecules and atoms. Nanomedicine is an emerging field that is expected to yield highly specific medical treatments for preventing disease and improving health.

Click HERE to download the course registration form

REGISTRATION AND GRANTS

Deadline for registration is October 12. The fee is 150 euros (includes lunches and coffee breaks). You can register here.

Grants will be available for PhD students to cover the registration fee. Closing date for application is October 7. Final results will be known October 13.

For more information, please contact Isabel Machado – isabel.machado@inl.int – Tel.: 253140112

NanoArt- Beautiful Images Taken at Nanoscopic Levels

NanoArt is a new art discipline related to micro or nanosculptures created by artists or scientists through chemical or/and physical processes are visualized with powerful research tools like Scanning Electron Microscopes. The microscope images are processed further using different artistic techniques to create pieces of art that can be showcased for the general public.

Sereval contest are organized each year in order to find the most beautiful NanoArt image. Click HERE to access the online exhibition for the 2011 NanoArt online Competition.

You can see some of the most beautiful NanoArt Images in the video bellow: