Fe4N is one of the attractive materials for spintronic devices due to its large spin asymmetric conductance and negative spin polarization at the Fermi level. We have successfully deposited Fe4N thin film with (001) out-of-plane orientation using a DC facing-target-sputtering system. A Fe(001)/Ag(001) composite buffer layer is selected to improve the (001) orientation of the Fe4N thin film. The N2 partial pressure during sputtering is optimized to promote the formation of Fe4N phase. Moreover, we have measured the ferromagnetic resonance (FMR) of the (001) oriented Fe4N thin film using coplanar waveguides and microwave excitation. The resonant fields are tested under different microwave excitation frequencies, and the experimental results match well with the Kittel formula. The Gilbert damping constant of Fe4N is determined to be α = 0.021±0.02. We have also fabricated and characterized the current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) device with Fe4N/Ag/Fe sandwich. Inverse giant magnetoresistance is observed in the CPP GMR device, which suggests that the spin polarization of Fe4N and Fe4N/Ag interface is negative.
Bibliographical noteFunding Information:
This work was supported by the C-SPIN center, one of six STARnet program research centers, a Semiconductor Research Corporation program, sponsored by MARCO and DARPA. Device fabrication was performed at the University of Minnesota Nanofabrication Center, which receives support from the National Science Foundation (NSF) through the National Nanotechnology Infrastructure Network program. Thin film characterization was performed at the University of Minnesota Characterization Facility, which has received capital equipment funding from the NSF through the Materials Research Science and Engineering Center.
© 2017 Author(s).