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Magnetization Dynamics Modeled in Magnetic Thin Films



Robert D. McMichael


One of the challenges facing designers of high data rate computer hard drives and magnetic memory chips is that for most magnetic metals, it typically takes a fewnanoseconds for the magnetization to come to rest after it has been switched or bumped by a magnetic field pulse. In hard drives, for example, the damping process is important for the write head that generates field pulses, the media that switch to record the field pulses as a magnetization pattern, and for the read headsensors that detect the fields from the recorded pattern. A nanosecond scale damping time makes it inherently difficult to design devices that will operate at data rates greater than 1 GHz. The most common technique to assess magnetizationdamping in magnetic films is to measure the ferromagnetic resonance line width of the material. However, films of interest are seldom perfectly uniform, and meas-ured line width reflects both the damping and the defects in the sample. NIST researchers have developed a line width model that takes the defects into account and predicts the changes in line width that would be observed based on the typeand strength of inhomogeneity. An earlier model of line width covers the limit ofvery small, weak defects where the magnetization is expected to behave mostly uniformly. In the opposite limit of strong, large defects, the magnetization wasexpected to behave differently in different parts of the film, but it has not been clear what size defect was necessary for this local behavior to take place. The newmodel bridges the theoretical gap between weak defect and strong defect limits and establishes the conditions needed for local behavior. The new model allows line width data to yield separate information about damping and non-uniformity, and for some data sets, limits may be placed on the defect sizes, thus allowing much better characterization of magnetic recording media, heads, and other devices designed for GHz applications.
Journal of Research of the National Institute of Standards and Technology
108 No. 2




McMichael, R. (2003), Magnetization Dynamics Modeled in Magnetic Thin Films, Journal of Research of the National Institute of Standards and Technology (Accessed June 21, 2024)


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Created March 1, 2003, Updated February 17, 2017