Colloquium

The Properties of Single Atoms and Nanomagnets at Surfaces

Andreas Heinrich,
IBM
Wednesday, November 9, 2005
Higgins 310, 4 pm

The magnetic properties of atoms are exploited in the IT industry to store binary information for long periods of time. The size of the magnetic bits in these devices is shrinking every year as a consequence of the increased demand for storage density. For example in a disk drive, these magnetic bits currently have minimum dimensions of the order of 10nm, approximately 40 atoms across.

The scanning tunneling microscope (STM) is a great tool to study nanoscale structures on surfaces with atomic resolution. Unfortunately, when a magnetic atom is placed on a metal surface it looses its basic magnetic character. Rather than keeping its inherent spin, the interaction with the metal’s conduction electron is so strong that a Kondo effect arises which can be seen by STM spectroscopy. However, the basic magnetic character can be recovered when the atom is placed on a thin insulator grown on a metal substrate. In such a case we can measure the energy required to flip the spin of a single atom in a high magnetic field.

In the future we would like to go from such studies of single magnetic atoms towards nanomagnets assembled with the control of STM atom manipulation. We can assemble complex structure with the help of the STM as will be discussed in some detail with the example of molecule cascades. In these cascades information is transported along a wire with the help of “falling” molecules. In addition to transporting information on the atomic scale, the intersections of these cascades can perform basic logic operations.

I will conclude by discussing a possible way of combining the surprising powers of molecule cascades with the intriguing possibilities of magnetic nanostructures. My hope is that one day we can build a computer where the information is stored magnetically on the processor and all logic operations are performed with the same magnetic nanostructures.