1 / 14

Magnetic Data Storage and Nanotechnology

Magnetic Data Storage and Nanotechnology. Hard Disk. Sensors Media. Switching layer 5 nm. Magnetic grain 10 nm. Faster than exponential. Technology Changes in Magnetic Data Storage. GMR Reading Head. 5 nm NiFe Optimum. Giant Magnetoresistance (GMR) and Spin Filters.

albert
Download Presentation

Magnetic Data Storage and Nanotechnology

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Magnetic Data Storage and Nanotechnology Hard Disk SensorsMedia Switching layer 5 nm Magnetic grain 10 nm

  2. Faster than exponential

  3. Technology Changes in Magnetic Data Storage

  4. GMR Reading Head 5 nm NiFe Optimum

  5. Giant Magnetoresistance (GMR) and Spin Filters Parallel Spin Filters  Resistance Low B>0 M Opposing Spin Filters  Resistance High B=0 M NiFe Cu Co • Two filtering mechanisms: • Bulk: Spin-dependent scattering (Scattering length ℓ>ℓ ) • Interface: Spin-dependent reflection(Spin-dependent potential step)

  6. GMR and TMR Reading Heads • General principle: • Two ferromagnetic layers separated by a non-magnetic layer. • For B=0 they have opposite magnetization (1800). • An external B-field forces them parallel (00). • The switch from opposite spin filters to parallel spin filters • reduces the resistance. • Obtain maximum sensitivity right at the switching point (900). • Implementation: • GMR = metallic spacer layer(Giant Magneto-Resistance) • TMR = insulating spacer layer(Tunnel Magneto-Resistance)

  7. (GMR) Current in plane (CIP) (TMR) Current perpendicular to the plane (CPP) TMR has taken over GMR in hard disk reading heads: Larger effect with the current perpendicular to the layers, no shorting by the metal layer. GMR vs. TMR

  8. Magnetic Storage Media Magnetic Force Microscope (MFM) Image Need 102 magnetic particles per bit to average out size and shape variations. Can’t make them smaller (next slide). The ultimate limit: one particle per bit ! 10 nm CoPt particles (magnetically isolated by a Cr coating)

  9. Flip Rate =fexp[-E/kT] = Attempt frequency  Larmor 109 s-1 40kT for several years retention frequency (proportional to the volume) (Lect. 24) Probability per attempt Superparamagnetic Limit of the Particle Size: Thermal Switching Energy Barrier E Preferred axis = “easy axis” (c-axis in hcp Co, shape anisotropy)

  10. B-field B-field A large external B-field costs energy. Close the field lines internally. (A more quantitative description requires the demagnetizing field Hd .) Magnetic Shape Anisotropy (Dipole Interaction) • Thin film: M parallel to the film • Rod-shaped particle: M parallel to the rod

  11. Unfavorable when shrinking bit size. More volume for the same area. Favored by the shape anisotropy.

  12. The next Step: Patterned Magnetic Storage Media: One Particle per Bit

  13. “Perfect” Magnetic Particles Can use fewer particles per bit FePt Nanocrystal with Organic Shell 3D stacking 2D stacking

More Related