In new research appearing in the journal Nature, physicists at Spain’s University of Alicante and at Rice University in Houston, USA have found that single-atom contacts made of ferromagnetic metals like iron, cobalt and nickel behave very differently from the slightly larger versions in the devices that are used in today’s electronic gadgets. The findings centre on the Kondo effect: metals such as copper conduct electricity better as they became colder, but the addition of even trace amounts of ferromagnetic metals such as iron prevents this. As explained by Kondo, this is because while cooling normal metals results in fewer vibrations among atoms, and thus less electrical resistance, mobile electrons in the metals tend to align their spins in the opposite direction of the spins of electrons in a magnetic atom. Thus, at low temperatures, an electron moving past a magnetic impurity will tend to flip its spin and therefore get deflected from its path. This explains why even tiny magnetic impurities can cause electrical resistance to rise, in spite of further cooling.
Based on decades of experimental evidence, physicists would not ordinarily expect the Kondo effect to play a role in wires and contacts made entirely of ferromagnetic metals like iron, cobalt and nickel. Yet that is precisely what this new rsearch found occurring in experiments with single-atom ferromagnetic contacts that were created by lowering and raising the tip of a scanning tunneling microscope onto a surface.

www.physorg.com/news160235209.html