The Nobel Prize in Physics 2007
Albert Fert, Peter Grünberg
Telephone interview with Albert Fert following the announcement of the 2007 Nobel Prize in Physics, 9 October 2007. The interviewer is Adam Smith, Editor-in-Chief of Nobelprize.org.
[Albert Fert] – Hallo?
[Adam Smith] – Hello, this is Adam Smith calling from the Nobel Foundation's website.
[AF] – Oh yes.
[AS] – Well, it's so nice to talk to you, and congratulations on yesterday's prize.
[AF] – Thank you.
[AS] – How have the last 24 hours been?
[AF] – Oh, the last? OK, many journalists, many TV, and trying to explain, simply, the science, the physics.
[AS] – It's daunting physics for people because it's quantum mechanics.
[AF] – But it's possible to explain simple things.
[AS] – The analogy that I've been using to try and explain what it is that is happening ...
[AF] – Yes?
[AS] – ... is the idea of crossed polaroids.
[AF] – Yes, exactly, yes.
[AS] – That you can consider electron spin to be the polarizers and when they're crossed they prevent the passage of current and when they're aligned they allow the passage of current.
[AF] – Yes, this is the good picture. Yeah, and the basic physics is what can be the polarizer for the spin of the electron.
[AS] – Yes, and the polarizer is the magnetic field?
[AF] – No, it's not the magnetic field, it's the magnetic material. And so the basic physics is; the influence of the spin on the mobility of the electron in magnetic materials. And so the concept of the GMR is to put on the way of the electrons a thin layer of magnetic materials, and this thin layer will be the polarizer, the two polarizers, or the mutli-polarizers. And so, because the magnetization can be controlled by the field, so this is also a way to detect the field, OK. But the intermediate between the field and the electrons, there is the magnetization of layers.
[AS] – Now this is an extension of the discovery made by William Thomson 150 years ago, and you discovered the new effect of giant magnetoresistance in 1988.
[AF] – Yes, in fact, between the observation you refer to, there was this physics. So the physics is the influence of the spin on the mobility of the electron in the magnetic material. This has been suggested by Mott, Sir Neville Mott, Nobel Prize, before the World War, and is something that I have confirmed, quantitatively, in my PhD. The defence was in '70. And so, the physics basis for my idea in this field came from all the results I got in my PhD and just after on the strong dependence of the conduction in magnetic material, dependence on the spin.
[AS] – Right.
[AF] – And so, I found that this dependence can be very strong if one dopes some materials with impurity, for example, and so I propose also what is called now the two current model of the conduction in magnetic materials. But at this time, say '70, '74, to proceed to the GMR was not possible because the GMR, in fact we had some concept at this time really close to the concept of the GMR, but to really find the GMR of the multilayer it would have been necessary to be able to fabricate multilayers with layers as thin as 1 or 2 nanometers, a few atomic layers, and this was not possible in the ‘70s.
[AS] – So it took the development of the technologies ...
[AF] – Yes, and so some ideas were put into the fridge during some time and then, with the progress in the technology of the deposition of layers, due to the microelectronics mainly, it became possible, in the mid ‘80s, to prepare such multilayers with very, very thin layers. And Peter Grünberg at this time, and myself, were more or less pioneers in the field of the fabrication of such nanostructures. You see the basic physics was ... and there is another important basic physics: before the GMR, first, so this spin-dependence of the conduction (my PhD and the work just after) and the work of Peter Grünberg who demonstrated in '86 that in multilayers of iron and chromium there was a coupling between two adjacent iron layers separated by chromium and this coupling make that the magnetization are in opposite directions, in the two iron layers. So it was possible with this system to get a system in which it was possible to change from parallel to anti-parallel polarizers. And so, by combining the idea of the conduction, the result of Grünberg, it was possible to find the GMR.
[AS] – To envisage that it was there and then to find it once the technology was available.
[AF] – This is a nice example of physics, science, advances frequently by the encounter between two domains, two different domains. The meeting between fundamental physics, on the conduction, and technological advances.
[AS] – So you have to be aware of what's happening in both fields?
[AF] – Yeah, yeah, yeah. And in fact, the nanotechnologists are a wonderful tool for the physicists, and for the biologists and for the chemists. Because this is a tool, this is not, nanotechnology is not really a science, this is a tool for us. We used this tool to discover the GMR. Now this tool of nanotechnology is used in many other aspects of spintronics because in my opinion, more important than the GMR and its application to the hard disk and so on, in my view more important is that this has opened the field of a new type of science with this spintronics, with many other effects related to the influence of the spin on the conduction.
[AS] – And this will lead to quantum computing, perhaps?
[AF] – Quantum computing is one of the axes, one of the roads, but now in spintronics, you have for example what is called the spin transfer phenomenon. So, in spin transfer you can manipulate the magnetization of a ferromagnetic body without applying a magnetic field but only by a sort of transfusion of spin angular momentum from an electrical current and this can be used either to switch the magnetization or to generate oscillations in the microwave frequency range. This is more or less exactly the contrary of the GMR. In the GMR you detect a magnetization with a current. In spin transfer, you create a magnetization with a current, a spin-polarized current, an electrical current with different numbers of spin-up and spin-down.
[AS] – And although this is still basic research, what do you see as the practical application of spintronics?
[AF] – Practical application? The next generation of MRAM, magnetic random access memory, will use the switching of the memories by spin transfer, this is already, very good results have been announced by Sony, for example, in Japan. Hitachi too. So, one application is the switching of magnetic devices and another application I am working on intensely now is the application to the emission of microwaves. To have very small emitters because by using oscillation of the magnetization by spin transfer, this oscillatory motion, one induces also an IC voltage in the gigahertz range and this is a way of producing oscillations, emitting microwaves. So there are many applications that can be expected in telecommunications.
[AS] – Basically these are microscopic transmitters that are being created?
[AF] – Yes, microscopic emitter, microscopic oscillator. In fact it's better to say oscillator, because it produces an electrical voltage in the gigahertz range.
[AS] – Where would you see these being used?
[AF] – For example, because these oscillators are very agile, flexible, you can tune the frequency by changing the current, the spin-polarized current, and so this can be a generation of very flexible oscillators, very flexible emitters. For example, in mobile phones you start from the oscillation in the megahertz range and after some doublings of frequency you can get the microwave range. But these emitters are directly oscillating in the gigahertz range, and also you can change easily the frequency, very easily the frequency, and so they should present a very flexible new generation of oscillators.
[AS] – That's very exciting stuff.
[AF] – Yeah, this is one of the axes in spintronics. You know, for the researcher, for the physicist, the past is the past but the more exciting is what is emerging now, OK. So I describe where is my excitation now.
[AS] – Yes, yes.
[AF] – So this road of spin transfer, also spintronics with semiconductors, towards a fusion between classical electronics and spintronics. Spintronics with molecules also is very promising,
[AS] – This is thrilling stuff, it's lovely to hear. Thank you for describing it. I should let you go soon, but I wanted just to return to the fact that you are the new French Laureate, and this will make you a celebrity. How do you feel about the prospect of being more of a celebrity now you have this Prize?
[AF] – The prospect for me?
[AS] – Yes.
[AF] – For me. OK, this is fantastic for me, but maybe for my team? So this certainly, all my young co-workers are very, very happy to be recognized, and that is recognition of the work of me and of the team. And so this certainly will help them in developing their research with me, of course. So this is a good opportunity, this is good for us.
[AS] – Yes, and good for the field, of course. Well, thank you very much indeed for this conversation. When you come to Stockholm in December to receive your Nobel Prize we interview Laureates again, so I hope we'll have a chance to talk again then.
[AF] – OK, so thank you.
[AS] – Well, thank you, very much indeed.
[AF] – And see you in December.
[AS] – See you in December, bye, bye.
[AF] – Bye.