Angular dependence of spin-transfer switching in a magnetic nanostructure

Abstract

We measured switching of a thin film nanomagnet driven by spin-polarized current in giant magnetoresistance spin valves as small as 50 nm×100 nm. Spin-transfer reversal is observed in both dc current and magnetic field sweeps, with a switching current of ∼5 mA, for example, for a bit with ∼900 Oe switching field in zero current. We studied the dependence of spin-transfer switching on the relative angle φ between the layer magnetizations by using a magnetic field to orient the magnetization of a bulk magnetic layer at an angle to a patterned layer held in place by shape anisotropy. The critical current is a minimum for collinear magnetizations and diverges as 1/|cos φ| as φ increases to 90°, consistent with switching current calculations using the Slonczewski spin-transfer torque model.

Large-amplitude coherent spin waves excited by spin-polarized current in nanoscale spin valves

“…The polarization direction θ p of the electron magnetic moments in the dc-current is expected to be one of the most important parameters of the problem. First, the onset threshold for oscillations should depend strongly on this polarization direction [55,69]. Second, the relative strength of the Oersted field (with respect to the spin torque magnitude a J ) also should depend on θ p , because the Oersted field for different θ p is computed assuming that the threshold value cr J a always corresponds to the experimentally measured critical current I cr ≈ 2.7 mA.…”

Micromagnetic computations of spin polarized current-driven magnetization processes

“…In addition to the theoretical works [1][2][3][4], several experiments on spin polarized current-driven magnetization reversal have confirmed the potential application of this effect in magnetic random access memories [5][6][7] as well as in novel devices like microwave sources or resonators [8].…”

Physical Principles of Spin Torque

“…It results from a partial cancellation of the total transferred spin angular momentum for a portion of the precession orbit of m when f 6 ¼ 0. [21,67].…”