A love of condensed matter experiments has been the constant of my wandering orbit through the physics universe.
The journey so far has included fun visits with:
quantum fluids and solids (3He),
epitaxially-grown magnetic semiconductors (femtosecond spin spectroscopy),
lithographically-patterned micro- and nano-ferromagnets (picosecond stroboscopic imaging),
and hybrid nanomagnetic/nanomechanical/nanophotonic systems (spin mechanics).
For better or worse I love equally developing new tools and applying them to answer the physical question that motivated their development, which usually leads somewhere unexpected
In grad school there was an older prof who would randomly appear in the student shop, make a quick part on a lathe or mill and be on his way. Somehow I could just tell, without knowing who he was or what the parts were for, that he was the person I most wanted to emulate in the very long term, if I was lucky enough to have that opportunity. He was Prof. Paul Hartman, who developed the senior undergrad/beginning grad student laboratory course at Cornell. I would love to leave behind the rudiments of a 4th year and grad hands-on experimental physics course before my turn at Alberta is up.
I am blessed with a wonderful spouse and four amazing adult children. In my spare time I am very much enjoying learning to sing and being gobsmacked by the experience of singing in a choir — which has put another outside passion (disc golf) on the back burner. One of the things I weirdly will never tire of is watching a spinning disc in flight. Others are optical interference, magnetic resonance, and bicycling. 2016-17 marked my 30th anniversary of year-round bike commuting (not including a 6 year gap when I worked at the IBM TJ Watson Research Center in Yorktown Heights, NY). Currently, I campaign a Karate Monkey fixie much of the year, and a Pugsley fatbike in the winter (go Surly!). In another life I might try to become a sailor, a bike mechanic, or try to start a Montreal-style bagel shop family business in Edmonton.
BSc Physics (Honours) University of Alberta (1981)
MSc Physics Cornell University (1984)
PhD Physics Cornell University (1988)
A big attraction of physics research is the quest for deeper understanding of how the world and universe work. Prof. Vinay Ambegaokar’s ready question for graduate students is: “What physical problem are you trying to elucidate?” Our group’s answer of the moment: what happens to angular momentum inside magnets.
Specifically, we are working on mechanical detection of magnetic resonance. You can’t make a magnetic dipole moment without angular momentum. This indeed is the reason why magnetic resonance and MRI are possible.
Long before magnetic resonance was discovered, one of the first experiments addressing angular momentum conservation in a magnet was performed on iron by Einstein and de Haas in 1915 (thought to be Einstein’s only experiment). How could this possibly still be a good question to work on today? Thanks to the new technologies we can bring to bear, it is. Larry Friedman, a senior graduate student of Bob Richardson told me in 1982, “You don’t have to look under many rocks to find something new”. One of the reasons this remains true is the steady development of new tools to help see new things under the same old rocks.
The University of Alberta is a terrific place to work on this topic of ‘spin mechanics’ thanks to our state-of-the-art laboratories and facilities like the nanoFAB, and collaborators on campus at NRC-NANO.
Einstein-de Haas effects represent fundamental physics that should be presented when magnetism is discussed in undergraduate textbooks. One of our related activities is to work towards updating the curricular coverage through experimental physics courses. The Science Hardware Makerspace (the Shack) allows students to have access to technologies for use in their own projects and courses more quickly than what’s typical at other institutions. SO much fun.
Our group strives to elucidate the physics of nanomagnetic and nanomechanical systems, through the development and application of sensitive measurements of individual nanostructures (ultrafast optical microscopy, scanning tunneling microscopy, nanomechanical magnetometry). Advanced nanofabrication methods are used to create the nanosystems.
‘The world’s smallest marriage proposal’
The ultimate motivation for the creation of this molecular-scale font was romance. Jacob Burgess and David Fortin completed it in time for Jacob to propose to his then-girlfriend, now-wife Allison. Each bump is an individual carbon monoxide molecule on an otherwise pristine copper surface, in ultrahigh vacuum at low temperature.
A microscopic garnet crystal was the key to unlocking the torque-mixing magnetic resonance spectroscopy technique reported in this issue.A focused gallium ion beam sculpted the single-crystal, one micrometer diameter yttrium iron garnet disk from within a much larger starting piece of the magnetic gemstone.The image is an angled-perspective scanning electron micrograph, showing the microdisk before it was placed on the nanomechanical sensor with which precise mechanical torque signatures of magnetic resonance were observed.
In an investigation of the speed limits for writing data on a magnetic hard drive, a large-scale (2 micron by 10 micron) representative memory element was caught in the act of switching by picosecond-resolved, stroboscopic magneto-optical imaging. The colour map represents the local direction of magnetic moment (blue = left, red = right). In the measurements shown here, switching is driven by a reversing field applied accurately parallel to the long-axis of the rectangle. In this geometry, there is no torque on the magnetization in the material when the field is first applied, but it has been made unstable — akin to balancing a pencil on its point. Unlike the pencil analogy, however, the magnetization is flexible — more like a ribbon standing on end — and responds to the instability by collapsing through a wavy buckling.
Choi et al., PRL 2001
Choi and Freeman, Science 2001
Less technical presentations:
Freeman, Physics in Canada 1998
Freeman, The Physics Teacher 2009