This week in cond-mat

Two brief mentions this week.

arxiv:0811.4491 - M. Häfner et al., Anisotropic magnetoresistance in ferromagnetic atomic-sized metal contacts
Over the last few years there's been quite an interest in the effect of magnetic fields on the electrical resistance of atomic-scale contacts between ferromagnetic metals (e.g., Ni). As pointed out by last year's Nobel in physics, if one can create nanostructures with very large magnetoresistive effects, there can be immediate applications in magnetic data storage. Recent investigations (for example, here and here) have shown dramatic variations in the magnetoresistance of such contacts from device to device. It's pretty clear that the atomic-scale details of the structures end up mattering (which is pretty cool, but rather discouraging from the technological side). This paper is a theoretical look at this issue, emphasizing that this sensitivity to details likely results from the fact that those last few atoms at the contact are undercoordinated - that is, they have fewer neighbors than atoms in the bulk of the magnetic metal.

arxiv:0812.0048 - Masubuchi et al., Fabrication of graphene nanoribbon by local anodic oxidation lithography using atomic force microscope
I've been waiting for a paper like this to show up. It's been known for about a decade now that one can use the tip of an atomic force microscope to do very local electrochemistry. This has been exploited to make interesting metal/metal oxide structures, designer surface details on Si, and impressive quantum dot systems in GaAs. These folks have done the same on graphene. Nice.
UPDATE: As was pointed out in the comments, I had overlooked two earlier reports of AFM oxidation of graphene, here and here.