Transcript from an interview with the 2007 physics laureates
Interview with the 2007 Nobel Prize laureates in physics Albert Fert and Peter Grünberg, 6 December 2007. The interviewer is Adam Smith, Editor-in-Chief of Nobelprize.org.
Albert Fert, Peter Grünberg, welcome to this interview for Nobelprize.org. You are the co-recipients of the 2007 Nobel Prize in Physics and often the work for which the Nobel Prize in Physics is awarded is very remote from everyday life, but in this case the giant magnetoresistance effect that you discovered touches us on a daily basis because it forms the memory retrieval system in most personal computers. I wanted to start by asking whether it was with thoughts of this sort of application that you embarked on the research?
Albert Fert: For me of course the discovery it was obvious that would be applications, but the width of this application was difficult to predict, it depends on the markets and on all these aspects that for me I did not know, so I was supposing there would be applications but the large number cannot be predicted.
But it was with an interesting application that you began the research or the research was done with other things in mind?
Albert Fert: No, the research was not done for the application, research in nano physics follows these ideas and discover new landscapes and when there is a new landscape the knowledge of this other perspective to go into and so on, it’s not a direct way to applications.
Peter Grünberg: But in our case, I can say, for us also the main goal was not to develop a sensor but when we found this effect, then the context was also that at that time similar senses were already in preparation for the application in our disk drives for IBM for example, and that was the so-called anisotropic magnetoresistance effect, When we measured for the first time this new effect which was later called giant magnetoresistance then we saw that this new effect was really much stronger than the anisotropic effect which also was already in preparation to be used in a sensor in hard disk drives. Then it was rather obvious then to file a patent and the application was really promising that this could be used.
It sounds as if in your case there may have been more thought of application on looking for the effect?
Peter Grünberg: Not when at the time when we started the research, then we just hoped to do interesting physics and get a new effect and so on. Of course we expected that there could be an effect between the parallel and antiparallel alignment of the magnetisation that the resistivity could change, we expected that, but we didn’t think of an application at that time yet but when we saw it really happen then we were very much encouraged also to find a patent.
It would be interesting to ask what lead you to physics and fundamental physics research in the first place. How did you become a physicist?
Peter Grünberg: At one point in high school I realised that this is a very interesting field and that was when I was always wondering why do the planets orbit around the sun and why is that notion. I couldn’t explain it to me until I heard the explanation of Newton, that it is the attraction between masses which keeps the planet on their orbits. I was so impressed by this discovery for me, that I wanted to hear more about this, about all these things and then I became very much interested in physics. I was the age of about 15 years old and then it remained like this, I stayed interested in physics.
That’s a good role model to start with, Newton as your guiding light.
Peter Grünberg: Yes, definitely.
And how about you?
Albert Fert: At the university I was a good student in physics, but I was hesitating before going into research because I was so impressed by the accumulation of outstanding research by outstanding people before, and it is difficult to realise that there is some space for a new researcher. I was hesitating and then I realised there was space for young researchers, and so many seemed to find to discover and this is a crucial part of physics, that if you are going into research there are many discoveries expecting for you.
What was that moment when you discovered – to your own satisfaction – that there was space for you?
Albert Fert: At the beginning of my PhD I was hesitating, not so confident, but then during my PhD my subject was to test some predictions of Sir Nevill Mott, a British Nobel Prize, it was suggesting that the spin cool have an influence on the mobility of the electron in ferromagnetic material sensor. This was to be proved and so we conceived with my supervisors some tests and so I realised that after these experiments, after a good interpretation, a very precise interpretation of experiments, it was possible to derive a clear picture of this subject and this clear picture is in fact is a basic physical spintronic study and so even during my PhD I have realised that it was possible to find something new in this.
Was the possibility of finding something new allowed by the technology?
Albert Fert: At this time no, it was allowed more by the progress of the theory in the group of Professor Friedel in France, the theory of the electronic structures in metals, so the progress was made possible by the theory. In fact in during my PhD we had some concept more or less the same as the concept of the GMR in ternary alloys, but at this time it was not possible in 1970 to go beyond and to go directly to the general magnetoresistance because it was not possible to fabricate multilayers in very very thin layers. We had simply to put some ideas into the fridge and in the mid-1980s I saw that the progress of the technology made that it was possible fabricate very very thin layers, so I came back into this field that I had […] known and I saw also the good result of Peter in 1986 on the coupling between the layers and this led me rapidly to the discovery of the GMR.
So that’s leaping ahead to the point which …
Albert Fert: This is due to the encounter between previous basic physics, fundamental physics and the advance of the technology, and the meeting produced the discovery.
Yes, nano technology had advanced officially.
Albert Fert: Nano technology is a wonderful tool for us because we are now able to, not only to observe the nature but also to fabricate a new nature, new objects with novel properties.
Returning to that idea of space for research, do you think that is something that changes in physics research? Is there more or less space for researchers as you go through the decades, or are all young physicists, do you think, at any times faced with similar questions: is there going to be space for me? What do you tell your students about this?
Albert Fert: I would say there is more space now than there’s been before. Because of nano technology, this is a wonderful tool to create.
So it’s easier now?
Albert Fert: Not easier, it is another tool, an additional tool for the creation, not only the observation.
Peter Grünberg: My impression is if I come nowadays to industrial laboratories, there are not many people anymore. There used to be many people, I had many colleagues for example at Siemens company and also some people at IBM and also I saw in fact the same ones in Japan. There are now many empty labs where people used to do research before and now they have closed these sections, so they concentrate more on the application and engineering.
Where is the fundamental research being done, is less being done or is it being done elsewhere?
Peter Grünberg: Probably it’s just less being done. Even in the research centres we have problems with staff, to fix positions for staff, so that is also being refused.
Is this a consequence of the fact that fundamental physics research is becoming more expensive and therefore there is just less money to go round?
Peter Grünberg: I don’t know the reasons, I only see empty labs.
Albert Fert: Because this is one reason, because the research become very expensive, the technologies …
Peter Grünberg: Yes, preparation, facilities, other expenses, and you really very much depend on such facilities, to have to make good samples if you want to have reliable results because it’s very important to have really good samples.
Is one result of this that physics is becoming concentrated in centres which have the power to pay for this, is it becoming more focussed?
Albert Fert: Yes certainly, only big companies for the research in the industry and also in some countries … I remember twenty years ago the research in South America, in small countries, was improving and catching up in research, but now the gap become larger. Because now it is only possible to make good research in some country with a very high technology and a lot of money, except maybe that there will be some country that will catch the others, China, India, Korea.
Does that provide then a nice flow of good young physicists from these countries coming in to the …?
Albert Fert: Yes, there is a lot of them, but there are also good labs in these countries, these new countries.
Peter Grünberg: Yes, for example there is an interesting tendency with China. About ten years ago when somebody applied from China to come to your lab and work there for some time you would expect that he never wants to go back to China, but now that has changed. Many many Chinese come and stay in Europe, probably also United States for some time but then they’re eager also to go back and there are also good positions for them, so definitely the situation in these countries is improving.
In your own careers were there particular people who made an enormous difference to the direction you took, who gave you guidance in a special way?
Peter Grünberg: I always worked with students and of course they are mostly newcomers or one can say, all the time newcomers in the field, so from that point of view you have to take the lead really, because you are continuously in some field and develop that and the students adjust to your subject and we discuss, but you have to take the lead.
But as a student yourself was there anybody who made a vast difference to your path, your choice of what you were going to work on or the way you worked on it? Did you have a mentor that was particularly important?
Peter Grünberg: Yes definitely, I had a mentor who defined the subject of my theses and then I worked on this. I still have contact with my mentor and hopefully he will also be here, come to the ceremony. Then I had many discussions with him while I was working on the subject, so one can say that, yes.
How about your professor Fert?
Albert Fert: My good luck during my PhD was that I was in the laboratory with a good mixing of experimentalists and theorists and the concept was to discuss with a foreign […]/ like me […] so I learned on both sides and this has been an advantage for me during my career. I was always able to proceed from experimental theory and some of my more cited papers are in theory, and so I think this was an advantage for me. Now I see that with the difficulty of the technology it’s more difficult for young people to be good on both sides, theory and experiments, so it was a good beginning.
Would you say you enjoy one more than the other – theory than experiment?
Albert Fert: No, I enjoy both, I enjoy physics in general, but it’s very gratifying to not only understand the experiment but at the same time to understand, deploy, the theory and to have a general view on both aspects.
How about you?
Peter Grünberg: That was a very similar situation for me too. Before I came into this transport phenomena and magnetoresistance, I studied a lot spinwaves and magnetic excitations in the […] structures. Then it was a very exciting experience for me that after some time the behaviour to do these calculations and predict such spinwaves and the frequencies of such spinwaves as a function of magnetic field or the orientation or in the field when you have anti-parallel alignment. Then at one point we were able to do a calculation simply by turning the one plus sign into a minus sign for the anti-parallel magnetisation in line and it was a very exciting moment for me to see that also in the experiment to see finally also the experiment shows that a calculation was really right, because when you do the calculation you never know whether you’ve made some mistakes or overlooked some boundary condition which does not allow to do this particular case because to violate some other laws. We were not sure but when we finally found those calculations correct from the experiment and this is a very exciting moment.
There must be rare moments when everything comes together, and the experiment proves what you thought. Is that the best bit of being a physicist, having these things happen, or is the best bit just being a physicist full stop?
Albert Fert: No, the marvel of physic is that for example you can start from pure abstract conscription in your mind and then is very gratifying and amazing to see that they become a concrete reality in the experiments and even more a concrete reality in the everyday life for, for the GMR. It is something fantastic to see that – something purely abstract become a reality of the life, that you see in the streets, in the shops. When you see for example a computer, we know that there is a hard disc working with something that we had in your mind 20 years ago and that this purely abstract thing became a device.
I wanted to ask you how it feels to spore the technology that is so widely used. It must be tremendously exciting to see it in use everywhere.
Albert Fert: Yes, amazing. It’s marvellous to see, that is the power of science, we see the power. I’ve been convinced, I was hesitating at the beginning of my career of what it could do, now I am convinced that science works.
Peter Grünberg: I am also very happy about the fact that this goes into an application that can be used for something. One can do very fine research, but then you always have to ask yourself is it really something, do we really learn something very new about nature and all these things, and in most of the case – when you are very critical – you say well, this is all in the old framework somehow, it’s not a complete jump into something which was completely unknown before, mostly not the case. Therefore, it’s very rewarding and satisfying if you have also an application for the kind of research you are doing.
Albert Fert: This is not unique for GMR. GMR gives a good example, an outstanding example, but in our career this happen several times and not for so large applications but for some less known discovery, but it’s exciting in any case, even for small discoveries. When you discover that you have predicted is a reality.
Let’s talk about GMR a little bit, but it’s quantum mechanics, so it’s difficult to comprehend. The idea that a magnetic field could affect a current was observed 150 years by Lord Kelvin. The magnitude of that effect was found to be possibly very much greater, or you discovered a very much greater effect than he discovered in the 1980s when you made your discoveries. Basically it’s to do with underlined or aligned electron spin, impeding current, and the model that I have been able to comprehend myself is the analogy with polarisers, that if electron spin – or the magnetic glare – is the polariser, crossed polarisers will impede for the flow of current, align polarisers will allow the flow of current, but I’d love to invite you to do a better description of GMR than that yourselves.
Albert Fert: The general idea of spin really is the general concept of spin […] is to put on the wheels on the electrons, this thin layer of ferromagnetic materials and to use the action of this thin layer of materials on the motion of the electrons. This is applied in GMR and in any of all the other effect of spintronics, this new image of polariser. He plays a magnetic field by something stronger that the electron can feel inside the ferromagnetic material you see. This corresponds to a multiplication by a very large factor of the affecting field acting on the spins.
Peter Grünberg: The picture of the polariser I think would have to be modified a little in that. In this picture of the polarisers the electrons move parallel to the polarisers, there is not a cross polariser situation which would apply for electrons which go mainly from one field to the other across the interlayer. This takes place too, but in that picture of the polariser our electrons move parallel to the polarisers and yet, since they travel back and forth during that drift after the current, there is some effect which could be also described by polarising effect, but the main motion of the electrons so to say in plain in parallel to the polariser in this picture as you described.
Albert Fert: But it was the first stage of spintronics, so it was, but in the new development of spintronics now, for a more efficiency the electrons are going through the magnetic layer.
So now the model becomes more appropriate.
Albert Fert: But it was not possible to do that technology […] in the beginning. The GMR was a […] way to approach the problem.
I suppose it doesn’t really matter if people understand how it works but what is interesting to them is to know how it will be used. We know about memory retrieval in hard disk drives, but the potential for GMR’s application is much wider than that. Would you like to speak a little about how you see GMR being used in the future?
Peter Grünberg: One application, and in fact I must say I didn’t even know about that application really, that came up doing all these discussions after the announcement of the Nobel Prize, people came to me: Oh, it is used in iPods, mp3 players, I didn’t know about that. So this is a very important application, I think, because these players are used everywhere, a huge application. It is being used, it will further being used, it will still be improved, but of course at some point probably there will be no more improvement, everything has physic limits. The density on hard disk drives has certain physic limits but then we will continue on a high level. But other applications of this magnetoresistance effect and that might be used one day in magnetic random access memories. This is in development now in the industry to achieve this.
This development, that relies on using current to induce a magnetisation rather than magnetisation to a changing current.
Albert Fert: This is a new development of spintronics because you can consider for the application of GMR first, so hard discs is the extension of the hard disc solution to mobile electronics, iPods, cameras and also medical applications. I have seen recently the application of GMR to encephalography, to the detection of the magnetic field generated by the brain. This is one side of the application, direct application of GMR, but the main result of GMR that is kicked off the theory of spintronics, a field looking for all the property related to the influences of the spin […] electrons. In spintronics there would be many other effects and is promising many other applications, for example … mainly walking on, under a type of effect called spin transfer for generation of radio waves, of micro waves, so this field of spin electronics has no real application not at all in the technology of computers but mainly on telecommunications. In fact now spintronics is expanding in many directions and with applications in many fields.
So this is for making nano scale transmitters?
Albert Fert: Yes, emitters, oscillators. In spin transfer experiments one manipulates the magnetisation, a magnet, without applying the magnetic field like traditionally, but by sort of transfusion of spins from an electrical current and this can be used to reverse the magnet. It is the contrary of the GMR, then one adds with the current on the magnet and also to generate oscillations and generate radio waves, microwaves, so this paves the way for many different applications.
This begs the question for me, when people come to work with you now on GMR and spintronics …
Albert Fert: GMR is passed.
GMR is finished, ok, GMR is done. When they come to work with you on spintronics and the further elaborations …
Peter Grünberg:: We have not seen that yet, I protest. GMR is not … There are still a lot of questions and interesting …
Albert Fert: There’s still questions but they are not so exciting now as new directions …
Peter Grünberg: I just wanted to make that comment.
When students come to work with you, because they have already seen the application potential of this, do you find that they are very focussed on application more than they should be, do you think?
Albert Fert: It depends on the students I guess, some are more attracted by the fundamental aspects, some now are attracted by the application, so there are different type of students.
So you still have the diversity, ok. It’s been very interesting talking to you, thank you very much indeed. I did want to ask one last question which was how the last two months have been. It’s a sudden whirlwind that starts when you hear the news that you have been awarded the prize. How have you found the last couple of months?
Peter Grünberg: Partly very tiring and I’ve had so many interviews, on the other hand it’s also nice to get some applause, it’s always nice. You are confirmed that this was the right way to do something and we have arrived at something, so a very good situation.
Albert Fert: There was a storm, there’s a big storm: interviews, many questions, conferences and also some responsibility, because now the people ask us for our advice on the reform of the research in our country and how to change the management of the universities, so new responsibilities. Many solicitations and I suppose we have learned to filter these things and to select only the most interesting requirements and requests.
Yes, I imagine you get very good at prioritisation.
Albert Fert: Yes, prioritisation.
Peter Grünberg: Many doors open which have been closed like now there is a magic stick, they are suddenly open. You are supported.
I shall leave you to your open doors that follow this interview. It was a great pleasure to talk to you. Peter Grünberg, Albert Fert, thank you very much indeed.
Albert Fert: Thank you.
Peter Grünberg: Thank you too.
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Nobel Prizes and laureates
Six prizes were awarded for achievements that have conferred the greatest benefit to humankind. The 12 laureates' work and discoveries range from proteins' structures and machine learning to fighting for a world free of nuclear weapons.
See them all presented here.