Enhanced magnetism in metal film sandwiches (invited)

The magnetic susceptibilities, χ, of Pd and Cr have been found to show very large enhancements in metal-film sandwiches of Au/Pd/Au and Au/Cr/Au. The enhancement arises from a combination of two factors: a narrowing of the density of states due to the thinness (∼1.5 nm) of the Pd and Cr films, and a stretching of the lattice by the Au. Stretching has been verified for the Au/Pd/Au films. Although the low density of states for Cr should limit such an enhancement, resistivity and susceptibility data are consistent with an antiferromagnetic transition at 2.4 K. Between 3 and 10 K, the temperature dependences of χ are approximately Curie-Weiss like for both Au/Pd/Au and Au/Cr/Au. The Au/Pd/Au and Au/Cr/Au data yield exchange enhancements of 400–28000 and ∼200, respectively. This makes Au/Pd/Au a possible candidate for p-wave-pairing superconductivity. Measurements seeking superconductivity at 0.010 K for Au/Pd/Au are described. No measurable χ is observed with Au/V/Au sandwiches, although surface spin fluctuations have been predicted.