High-speed switching and rotational dynamics in small magnetic thin-film devices
Stephen E. Russek, Shehzaad F. Kaka, Robert D. McMichael, Michael J. Donahue
The intent of this chapter is to review high frequency magnetic device measurements and modeling work at NIST which is being conducted to support the development of high-speed read sensors, magnetic random access memory, and magnetoelectronic applications (such as isolators and microwaves components). The chapter will concentrate on magnetoresistive devices, those devices whose resistance is a function of the magnetic state of the device, which can in turn be controlled by a magnetic filed. The low-frequency characteristics of magnetoresistive devices will be reviewed. Simulated high-frequency device dynamics, using single-domain and micromagnetic models, will be discussed. Next, high-speed measurements of magnetization rotation and switching in micrometer-size devices will be presented. The effects of thermal fluctuations and disorder on device dynamics will be examined, and high-frequency magnetic noise data will be presented. Finally, the need to understand and control high-frequency magnetic damping will be discussed, and a method for engineering high-frequency magnetization damping using rare-earth doping will be presented.