Spin-polarized current induced magnetization switch: Is the modulus of the magnetic layer conserved? (invited)

Abstract

The direct effect of spin-polarized current on magnetization states is studied on various electrodeposited single contacted nanowires (diameter about 60 nm). Three kinds of samples have been studied: (1) Homogeneous Ni nanowires, (2) nanowires composed of both a homogeneous Ni part and a multilayered Co(10 nm)/Cu(10 nm) part, (3) pseudospin-valve pillars Co(30 nm)/Cu(10 nm)/Co(10) electrodeposited in Cu wires. The magnetization reversal due to the current injection is observed in the three cases. The effect is observed with using different experimental protocols, including current activated after-effect measurements. The results obtained suggest that two different mechanisms are able to account for the magnetization reversal: exchange torque and spin transfer. We propose a definition of the two mechanisms based on the conservation or nonconservation of the magnetic moment of the ferromagnetic nanostructure.

Current-driven switching of exchange biased spin-valve giant magnetoresistive nanopillars using a conducting nanoprobe

“…In the measurements in this study, when the current was flowing from the thinner top CoFe layer to the thicker bottom CoFe/ NiFe layer, the resistance changed from a higher state to a lower one. The observed ⌬R/R was 2.7%, which is in line with the spin-transfer torque-driven switching reported elesewhere [5][6][7][8][9][10] for Co/ Cu/ Co nanopillars, as predicted by Slonczewski's model. 1 The critical current values are Ic + ϳ 6.5 mA and Ic − ϳ −7 mA which correspond to Jc + = 8.3ϫ 10 7 A/cm 2 and Jc − = 8.9ϫ 10 7 A/cm 2 , respectively.…”

Current-Induced Two-Level Fluctuations in Pseudo-Spin-Valve (Co/Cu/Co) Nanostructures

“…Two experimental approaches are preferred, sweeping the magnetic field H or the applied current I in order to obtain R(I), R(H), dV /dI(H) or dV /dI(I). Alternatively, observations of the relaxation of the magnetization [14,15,16] provide information on the magnetic energy profile.…”

Micromagnetic Simulation of Spin Transfer Torque Magnetization Precession Phase Diagram in a Spin-Valve Nanopillar under External Magnetic Fields

“…This mechanism of STT was initially proposed by Berger et al [8] and Slonczewski [9] in 1996 and attracted significant interests because of the great potential for direct current-induced spintronic devices [10][11][12]. The role of STT in magnetization switching has been verified by numerous experiments in spin-valve nanopillars [13][14][15], magnetic nanowires [16,17], point contact geometry [18][19][20], and magnetic tunnel junctions [21][22][23][24]. The most attractive application of currentinduced magnetization switching is magnetic random-access memory (MRAM), which has the advantages of nonvolatile, high addressing speed, low-energy consumption, and avoidance of cross writing.…”