MIT, Nature and a Double Bass

Sander Kamerbeek, a PhD student in the Physics of Nanodevices Group (Zernike Institute for Advanced Materials), has just had the results of his Master’s internship at MIT published in Nature. He clearly remembers the big breakthrough: ‘It was three in the morning when I called my supervisor and said, “you’d better come to the lab right now!”’

Sander studied Applied Physics at the University of Groningen, earning first his Bachelor’s and then his Master’s degree. ‘I love physics,’ he says, ‘because it answers so many questions about the world around us, like why the sky is blue. But it also shows you that if you were to tinker just slightly with some physical constants, you’d create a situation in which our universe couldn’t exist at all.’

But physics isn’t his only passion. ‘I seriously considered the academy of music. I play the double bass; it’s a very important part of my life. But I realized that while music could be a hobby, physics isn’t something you can do on the side.’ So he decided to study physics, and play the double bass in his spare time. ‘At the moment I’m in Dutch Spirit, an amateur big band, as well as a jazz trio.’

Sitting in his office at Nijenborgh 4, Sander recalls how he ended up at MIT. ‘Most of my friends managed to find internships somewhere interesting, like Japan, Singapore or the USA. You can also do your internship at a private company, which wasn’t the case with the Master’s thesis. My first choice was an IBM lab in the States, but that fell through.’

He had already done several projects at the Physics of Nanodevices Group when a new staff member, Tamalika Banerjee, who had worked with an MIT professor, suggested Sander join that group. ‘She recommended me, and I was accepted. So in November 2010 I found myself in Boston, where I knew just one person, a postdoc from Groningen. I didn’t even have a clear idea of my project. But if you don’t take risks, you won’t get anywhere.’

It all turned out fine. He was well received and found there were more international students on internships in his group. ‘We regularly did things together. Everyone put in long days in the lab, from about nine in the morning to seven in the evening, but we often took long breaks as well. So we’d take an hour for lunch or go out together after work.’

Now for the technical bit – if you’re a technophobe you might want to skip this bit and join us later for the grand finale.

Sander’s job was to use new molecules to build specific devices. ‘Basically, we were working on new data-storage techniques.’ The device he was working on consisted of two ferromagnetic electrodes that were separated by a non-magnetic spacer. The electrodes had what is termed a magnetic moment. If you imagine two stacked bar magnets, they might be aligned (north and south poles on the same side) or reverse-aligned (one with the north pole on the left, the other with the north pole on the right). In contrast to a bar magnet, which has a fixed magnetic alignment, the magnetic moment of the two electrodes in Sander’s device could switch.

‘Now when you pass a current through the device, the resistance is lowest when the magnetic moment in the electrodes has the same orientation.’ By switching the magnetic moment in one of them, you can alter the resistance. ‘You’ve therefore created a way to store and read binary information using high or low resistance.’ Such devices are promising, but as yet too complicated to be of any real use.

The spacer between the two ferromagnetic electrodes is an important part of the device. ‘It shouldn’t affect the current that passes through and can’t be magnetic.’ It was Sander’s job to test a new compound for this spacer in a thin layer of about a hundred molecules. When he began testing the devices he’d made, strange things started to happen.

‘The measurements just weren’t as expected. Normally, you’d see a change in resistance when you reverse the magnetic moment of one magnet and again when you reverse it in the other magnet. But at first, I only saw one change.’ The technical details are rather complicated, but it turned out that the spacer was acting as a third magnet. ‘That was surprising, because the material didn’t have any magnetic properties. But when you had this very thin layer on top of a magnet, it did.’

If you skipped the technical bit, welcome to the grand finale.

Sander performed the crucial experiment in the early hours of the morning. ‘I made the devices with electrodes and spacers myself, but they didn’t always perform well. So if you’ve got one that works really well, you carry on taking measurements for as long as you need.’ An added complication is that the devices were tested at around minus 269 degrees Celsius, using liquid helium to provide the low temperature. ‘Once the helium in the system runs out, the device gets warmer and might break apart. So you can’t stop for the night.’

It was at three or four in the morning when Sander saw some interesting results. ‘I knew this was important, so I phoned my supervisor and said, “you’d better come to the lab right now!” He only needed ten minutes to get there.’ The discovery led to a new concept for storing data – again, the details are rather technical, but suffice it to say that Sander’s work paves the way for storing data at a molecular level. And that means a 1000-fold increase in storage density on your hard disk. ‘MIT has even taken out a patent on the discovery.’

Sander is now working on his PhD thesis on nanodevices at the University of Groningen. He still has two-and-a-half years to go. And afterwards? ‘No idea. I love research, but that isn’t my only interest.’ He’ll be playing his double bass again at Jazz café De Spieghel on 19 February. Just for the fun of it.

Read more about the Nature article in this MIT press release – or in the Nature article itself: ‘ Interface-engineered templates for molecular spin memory devices ’