Quantifying spin-lattice relaxation rates in ferromagnetic transition metals

Keith Gilmore^1,2, Mark Stiles², and Eric Shirley¹

¹ Optical Technology Division, NIST Gaithersburg, MD 20899.

² Center for Nanoscale Science and Technology, NIST Gaithersburg , MD 20899

Magnetization dynamics plays an important role in the information storage and manipulation industry.  Despite their critical importance, dynamic processes in magnetic systems lack a predictive understanding.  This lack is hindering the evolution of magnetic storage allowing non-magnetic memory systems to encroach upon the market.  To enhance the development of magnetic memory technologies, we seek to uncover the fundamental physical mechanisms that drive magnetization dynamics.          

Conventional practice treats magnetization dynamics as damped rotations with a fixed magnetization magnitude.  The damping rate, which quantifies the rate of exchange of energy and angular momentum between the magnetization and the lattice, is the quantity of primary interest.  This damping rate has long been treated as a phenomenological parameter, discernible only through measurement.  However, we have recently identified the spin-orbit interaction as the primary mechanism responsible for damping in bulk transition metal systems and have demonstrated the ability to accurately calculate damping rates from first-principles.

Recent experiments have probed a realm of magnetization dynamics in which the magnetization no longer evolves with constant magnitude.  These observations have been most dramatic for revealing previously unknown dynamics on femtosecond timescales.  Understanding and controlling dynamics on these timescales open the possibility of increasing the speed at which information is manipulated by orders of magnitude.  We will present our research plan for performing first-principles investigations into this new and exciting field.

CATEGORY: Physics

Mentors Name: Mark Stiles

Center for Nanoscale Science and Technology

A235, 216 Stop 6202

Tel: 301.975.3745

Fax:

Email: mark.stiles@nist.gov

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Mentors Name: Eric Shirley

Optical Technology Division

B210, 221 Stop 8441

Tel: 301.975.2349

Fax:

Email: eric.shirley@nist.gov