Controlled Normal and Inverse Current-Induced Magnetization Switching and Magnetoresistance in Magnetic Nanopillars

Abstract

By combining pairs of ferromagnetic metals with the same or different signs of scattering anisotropies in ferromagnetic-nonmagnetic-ferromagnetic metal nanopillars, we independently invert just the magnetoresistance, just the direction of current-induced magnetization switching, or both together, at room temperature (295 K) and at 4.2 K. In all cases studied, the switching direction is correctly predicted from the net scattering anisotropy of the fixed ferromagnet, including both bulk and interfacial contributions.

Spin transfer switching and low-field precession in exchange-biased spin valve nanopillars

“…5,7,8,[12][13][14][15] The devices reported here have been fabricated by a simple and reliable procedure based on using 3-D focused ion beam (FIB) milling. 17 Since in this process all the metal layers are deposited in a single ultra high vacuum cycle, excellent interface cleanliness is achieved.…”

Spin-Dependent Phenomena in Magnetoelectronic Devices

“…When, however, the spin asymmetries of both layers have opposite signs, the resistance is larger in the parallel configuration and smaller in the antiparallel one (inverse GMR effect). Both, normal and inverse GMR effects have been observed experimentally [7].…”

“…Figure 1 implies that a positive current (I > 0) tends to destabilize the parallel configuration and can switch it to antiparallel one when current exceeds a certain threshold value. On the other hand a negative current tends to destabilize the antiparallel configuration and stabilize the parallel one [5,7]. When positive current (flowing from the reference towards the sensing layer) causes transition to antiparallel magnetic configuration, the switching is known as normal CIMS.…”

Electrical Control of Magnetic States

“…This appears as a torque exerted locally on the magnetization. In spin valve structures the spin-transfer torque may lead to the phenomenon of current-induced magnetic switching (CIMS), predicted first theoretically [7,8], and then confirmed experimentally [9,10]. The magnetic switching can be detected via resistance measurements owing to the GMR effect.…”

“…This nonequivalence of spin channels has further consequences for transport properties of spatially nonuniform magnetic structures. Apart from the magnetoresistance phenomena (like the GMR effect), charge current in such systems is associated with spin current, and the latter can lead to magnetization switching between two stable magnetic states [7][8][9][10] or to stationary precessional states [11,12].…”