Tunable magnetization and damping of sputter-deposited, exchange coupled Py|Fe bilayers

Observation of Pure-Spin-Current Diodelike Effect at the Au/Pt Interface

Asymmetric charge transport at the interface of two materials with dissimilar electrical properties, such as metal-semiconductor and p-n junctions, is the fundamental feature behind modern diode and transistor technology. Spin pumping from a ferromagnet into an adjacent nonmagnetic material is a powerful technique to generate pure-spin currents, wherein spin transport is unaccompanied by net charge transport. It is therefore interesting to study pure-spin transport at the interface of two materials with different spin transport properties. Here we demonstrate asymmetric transport of pure-spin currents across an interface of dissimilar nonmagnetic materials Au/Pt. We exploit Py/Au/Pt/Co structures where spin pumping can generate pure-spin current from either Py or Co independently. We find that the transmission of pure-spin current from Au into Pt is twice as efficient as transmission from Pt into Au. Experimental results are interpreted by extending conventional spin-pumping, spin-diffusion theory to include boundary conditions of reflected and transmitted spin current at the Au/Pt interface that are proportional to the established spin chemical potentials on either side of the interface.

Study of the magnetic interface and its effect in Fe/NiFe bilayers of alternating order

We present a comprehensive study on the magnetization reversal in the Fe/NiFe bilayer system by alternating the order of the magnetic layers. All the samples show growth-induced uniaxial magnetic anisotropy due to the oblique angle deposition technique. Strong interfacial exchange coupling between the Fe and NiFe layers leads to single-phase hysteresis loops in the bilayer system. The strength of coupling being dependent on the interface changes upon alternating the order of magnetic layers. The magnetic parameters such as coercivity H_C, and anisotropy field H_K become almost doubled when a NiFe layer is grown over the Fe layers. This enhancement in the magnetic parameters is primarily dependent on the increase of the thickness and magnetic moment of the Fe–NiFe interfacial layer as revealed from the polarized neutron reflectivity (PNR) data of the bilayer samples. The difference in the thickness and magnetization of the Fe–NiFe interfacial layer indicates the modification of the microstructure by alternating the order of the magnetic layers of the bilayers. The interfacial magnetic moment increased by almost 18% when the NiFe layer was grown over the Fe layer. In spite of the different values of anisotropy fields and modified interfacial exchange coupling, the Gilbert damping constant values of the ferromagnetic bilayers remain similar to the single NiFe layer.

We deposited Fe/NiFe bilayers using magnetron sputtering and studied their static and dynamic properties. We performed PNR measurements and investigated whether the interfacial exchange coupling is responsible for the tuning of the magnetic properties.