We derive spin-diffusion lengths at 4.2 K in sputtered Pd and Pt of lsfPd=25−5+10 nm and lsfPt=14±6 nm, interface specific resistances of sputtered Pd/Cu and Pt/Cu of 2ARPd/Cu=0.9±0.1 fΩ m2 and 2ARPt/Cu=1.5±0.1 fΩ m2, and the amount of spin-memory loss at the Pd/Cu and Pt/Cu interfaces as δPd/Cu=0.24−0.03+0.06 and δPt/Cu=0.9±0.1. We compare our values with those from metals in similar rows of the Periodic Table, Nb for Pt and W for Pd.

No abstract

The series resistor and Valet-Fert models widely used to describe the current-perpendicular-to-plane ͑CPP͒ magnetoresistances of ferromagnetic/nonmagnetic ͑F/N͒ metal multilayers were recently claimed to be valid only for mean-free paths shorter than layer thicknesses; otherwise the mean-free path was claimed to be an important length scale in the CPP magnetoresistance ͑MR͒. This claim was based on observations of differences in the CPP MR's, after the samples were taken to above their saturation magnetic fields, of two different kinds of multilayers involving Co and Cu: interleaved ͓Co(6)/Cu(20)/Co(1)/Cu(20)͔ N and separated ͓Co(6)/Cu(20)͔ N ͓Co(1)/Cu(20)͔ N , with N repeats and thicknesses in nm. The maximum CPP MR's of separated samples were only about half as large as those for interleaved ones. In two short papers, we provided experimental evidence that mean-free paths are not important length scales in the CPP MR by showing that the differences in CPP MR's upon which the above claim was made did not change when the mean-free paths in the N and F layers were reduced from well above to well below their layer thicknesses. We ascribed part of the behaviors of interest to finite spin-memory loss ͑spin flipping͒ in the F and N metals, and proposed that the rest might be due to spin flips at F/N interfaces. In the present paper we ͑a͒ present further experimental evidence against mean-free-path effects, ͑b͒ provide details of the calculations we use to analyze the data, and ͑c͒ use measurements of magnetization and polarized neutron reflectivity to show that the differences in CPP MR are not due to spurious differences in magnetic structure between interleaved and separated multilayers, but only to the differences in the relative magnetic alignment of adjacent layers. Additional evidence for this last point is our observation that the CPP MR's of separated samples in their as-prepared states are as large as those of the equivalent interleaved samples after they are taken to above their saturation fields. We show that similar differences between interleaved and separated data appear also in the current-in-plane ͑CIP͒ MR's and when the Cu is replaced by Ag.

This paper describes a method for creating a topography-based gradient on a metallic surface to help mitigate problems associated with condensate retention. The gradient was designed to promote water droplet migration toward a specified region on the surface which would serve as the primary conduit for drainage using only the roughness of the surface to facilitate the movement of the droplets. In this work, parallel microchannels having a fixed land width but variable spacing were etched into copper substrates to create a surface tension gradient along the surface of the copper. The surfaces were fabricated using a 355 nm Nd:YVO4 laser system and then characterized using spray testing techniques and water droplet (2-10 μL) injection via microsyringe. The distances that individual droplets traveled on the gradient surface were also measured using a goniometer and CCD camera and were found to be between 0.5 and 1.5 mm for surfaces in a horizontal orientation. Droplet movement was spontaneous and did not require the use of chemical coatings. The theoretical design and construction of surface tension gradients were also explored in this work by calculating the minimum gradient needed for droplet movement on a horizontal surface using Wenzel's model of wetting. The results of this study suggest that microstructural patterning could be used to help reduce condensate retention on metallic fins such as those used in heat exchangers in heating, ventilation, air-conditioning, and refrigeration (HVAC&R) applications.

No abstract