CPM Seminar

FMR spectrum of an individual spin-valve device measured by FMRFM

Grégoire de Loubens

Service de Physique de l'État Condensé
CEA Saclay

The study of the dynamics of spintronics devices and in particular the influence of a spin polarized current on the emission spectrum of magnetic multilayers is of considerable interest [1-3]. From a fundamental point of view, the exact microscopic mechanism is still unknown, whereas the spin transfer effect is very promising considering the potential applications (MRAM, integrated RF oscillators).

I have used FerroMagnetic Resonance Froce Microscopy to measure the coherent excitation spectrum of an individual spin-valve device. This technique [4, 5] uses a magnetic probe fixed at the free end of a cantilever to measure the change in the static component of the dipolar field of the sample induced by the magnetization precession at resonance.

FMRFM is the only technique that has the sensitivity to detect the FMR signal of an individual nano-pillar. I will present results obtained on Permalloy samples in presence of a DC current. I will also show the modifications due to non-linear effects that become dominant at large excitation power [6].

[1] J.C. Slonczewski, J. Magn. Magn. Mater. 159, 1 (1996)
[2] L. Berger, Phys. Rev. B 54, 9353 (1996)
[3] S.I. Kiselev, J.C. Sankey, I.N. Krikorotov, N.C. Emley, R.J.Schoelkopf, R.A. Buhrman, and D.C. Ralph, Nature 425, 380 (2003)
[4] Z. Zhang, P.C. Hammel, and P.E. Wigen, Appl. Phys. Lett. 68, 2005 (1996)
[5] V. Charbois, V. V. Naletov, J. Ben Youssef and O. Klein, Appl. Phys. Lett. 80, 4795 (2002)
[6] G. de Loubens, V.V. Naletov et O. Klein, Phys. Rev. B 71, 180411(R) (2005)