Spin-torque ferromagnetic resonance measurements of damping in nanomagnets

The authors directly measure the magnetic damping parameter α in thin-film CoFeB and Permalloy (Py) nanomagnets at room temperature using a recently developed ferromagnetic resonance technique where the precessional mode of an individual nanomagnet can be excited by microwave-frequency spin-transfer torque and detected by the giant magnetoresistance effect. The authors obtain αCoFeB=0.014±0.003 and αPy=0.010±0.002, values comparable to measurements for extended thin films, establishing that patterned nanomagnets can exhibit magnetic damping that is consistent with that of unpatterned bulk material.

[1]  R Urban,et al.  Gilbert damping in single and multilayer ultrathin films: role of interfaces in nonlocal spin dynamics. , 2001, Physical review letters.

[2]  William J. Gallagher,et al.  Development of the magnetic tunnel junction MRAM at IBM: From first junctions to a 16-Mb MRAM demonstrator chip , 2006, IBM J. Res. Dev..

[3]  Gang Xiao,et al.  The role of electron scattering in magnetization relaxation in thin Ni$_{81}$Fe$_{19}$ films , 2002, cond-mat/0208207.

[4]  A. Brataas,et al.  Enhanced gilbert damping in thin ferromagnetic films. , 2001, Physical review letters.

[5]  Current-driven ferromagnetic resonance, mechanical torques, and rotary motion in magnetic nanostructures , 2006, cond-mat/0609258.

[6]  S. Yuasa,et al.  Spin-torque diode effect in magnetic tunnel junctions , 2005, Nature.

[7]  Dynamic stiffness of spin valves , 2002, cond-mat/0212130.

[8]  T. Miyazaki,et al.  Effect of spin diffusion on Gilbert damping for a very thin permalloy layer in Cu/permalloy/Cu/Pt films , 2002 .

[9]  M. De Graef,et al.  Demagnetization factors for elliptic cylinders , 2005 .

[10]  D. Ralph,et al.  Time-Domain Measurements of Nanomagnet Dynamics Driven by Spin-Transfer Torques , 2005, Science.

[11]  Matthew Carey,et al.  Spin transfer switching of spin valve nanopillars using nanosecond pulsed currents , 2005 .

[12]  I. N. Krivorotov,et al.  Large-amplitude coherent spin waves excited by spin-polarized current in nanoscale spin valves , 2007 .

[13]  Pavel Kabos,et al.  Control of magnetization dynamics in Ni/sub 81/Fe/sub 19/ thin films through the use of rare-earth dopants , 2001 .

[14]  S. Adam,et al.  Theory of the spin-torque-driven ferromagnetic resonance in a ferromagnet/normal-metal/ferromagnet structure , 2006, cond-mat/0607145.

[15]  Mark D. Stiles,et al.  Magnetic normal modes of nanoelements , 2005 .

[16]  S. Yuasa,et al.  Characterization of growth and crystallization processes in CoFeB /MgO/CoFeB magnetic tunnel junction structure by reflective high-energy electron diffraction , 2005 .

[17]  D. Ralph,et al.  Spin-transfer-driven ferromagnetic resonance of individual nanomagnets. , 2006, Physical review letters.

[18]  J. Katine,et al.  Time-resolved reversal of spin-transfer switching in a nanomagnet. , 2004, Physical review letters.

[19]  Bernard Dieny,et al.  Excitations of incoherent spin-waves due to spin-transfer torque , 2004, Nature materials.

[20]  Time-resolved spin-torque switching and enhanced damping in permalloy/Cu/permalloy spin-valve nanopillars. , 2005, Physical review letters.

[21]  J. Katine,et al.  Thermal effects on the critical current of spin torque switching in spin valve nanopillars , 2007 .

[22]  R. Rosenfeld.  Nature , 2009, Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery.

[23]  Claude Chappert,et al.  Study of the dynamic magnetic properties of soft CoFeB films , 2006 .

[24]  N. Smith.  Modeling and measurement of spin torques in current-perpendicular-to-plane giant magnetoresistive (invited) , 2006 .

[25]  Ilya Krivorotov,et al.  Reducing the critical current for short-pulse spin-transfer switching of nanomagnets , 2005 .

[26]  G. Woltersdorf,et al.  Gilbert Damping in Single and Multilayer Ultrathin Films , 2001 .