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The ultimate speed of magnetic switching in granular recording media

Nature volume 428, pages 831–833 (2004)Cite this article

Abstract

In magnetic memory devices, logical bits are recorded by selectively setting the magnetization vector of individual magnetic domains either ‘up’ or ‘down’. In such devices, the fastest and most efficient recording method involves precessional switching1,2,3,4: when a magnetic field Bp is applied as a write pulse over a period τ, the magnetization vector precesses about the field until Bpτ reaches the threshold value at which switching occurs. Increasing the amplitude of the write pulse Bp might therefore substantially shorten the required switching time τ and allow for faster magnetic recording. Here we use very short pulses of a very high magnetic field5 to show that under these extreme conditions, precessional switching in magnetic media supporting high bit densities no longer takes place at well-defined field strengths; instead, switching occurs randomly within a wide range of magnetic fields. We attribute this behaviour to a momentary collapse of the ferromagnetic order of the spins under the load of the short and high-field pulse, thus establishing an ultimate limit to the speed of deterministic switching and magnetic recording.

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Figure 1: Magneto-optic patterns of magnetization.
Figure 2: Magnetic order parameter Mn(R).
Figure 3: Spin motion in a magnetic grain.

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Acknowledgements

We thank R. Iverson, C. Field and G. J. Collet for their assistance in preparing and carrying out the sample exposure at FFTB, and A. Vaterlaus for help with imaging the magnetic patterns. This work was carried out at the Stanford Linear Accelerator Center, which is supported by the Office of High Energy and Nuclear Physics of the US Department of Energy (DOE). The experimental programme of the SSRL authors is funded by the Office of Basic Energy Sciences of DOE.

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Authors and Affiliations

  1. Stanford Synchrotron Radiation Laboratory, PO Box 20450, Stanford, California, 94309, USA

    I. Tudosa, C. Stamm, H. C. Siegmann & J. Stöhr

  2. Landau Institute for Theoretical Physics, Kosygin str. 2, 117940, Moscow, Russia

    A. B. Kashuba

  3. Stanford Linear Accelerator Center, Stanford University, Stanford, California, 94309, USA

    F. King

  4. Seagate Technology LLC, Pittsburgh, Pennsylvania, 15222, USA

    G. Ju, B. Lu & D. Weller

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  1. I. Tudosa
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  2. C. Stamm
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Corresponding author

Correspondence to J. Stöhr.

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The authors declare that they have no competing financial interests.

Supplementary information

Supplementary Information

A table summarizes data with a variety of different recording media. Four figures show grain size distribution, magneto-optic patterns, mean switching mode, and mechanism of magnetostatic coupling respectively. (PDF 558 kb)

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Tudosa, I., Stamm, C., Kashuba, A. et al. The ultimate speed of magnetic switching in granular recording media. Nature 428, 831–833 (2004). https://doi.org/10.1038/nature02438

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