Tunneling magnetoresistance of CH4 and C2H4molecules sandwiched between Co clusters

Spin-dependent transport through individual molecules can be studied by tunneling magnetoresistance (TMR) measurements on samples made of metallic magnetic clusters embedded in molecular matrices. The TMR of Co clusters (mean cluster size 4.5 nm) embedded in CH 4 and C 2 H 4 matrices has been studied as a function of Co cluster volume fraction υ C o . While the TMR of Co/CH 4 is independent of υ C o , the TMR of Co/C 2 H 4 strongly decreases with increasing υ C o or decreasing mean tunneling barrier width s. This unexpected result can be explained in the following way: the orientation of the C 2 H 4 molecule sandwiched between two Co clusters changes with changing s; the interaction between the C 2 H 4 molecule and the Co cluster strongly depends on its orientation relative to the Co cluster surface. This results in a change of the character of the tunneling electrons with changing molecular orientation.