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Erasers: Single

Eraser – Single Disk

Media Preconditioning


Preconditioning with a write head is a slow process. For spin stand metrology, preconditioning with a head can be easily incorporated into existing tests. It complicates and lengthens the evaluation of read-write properties but is manageable. For drive builds, this can be a time consuming and costly process unless a wide write head is employed.

 We can design and produce permanent magnet single disk erase tools to fully precondition media post sputter.  Our magnetic material selection and circuit design expertise guarantees a device that meets magnetic field specifications within the physical limitation of existing or new equipment. In addition, our familiarity with HDDR devices and clean room compatibility requirements assures that the final device will be manufactured compliant to cleanliness and ESD specifications.


Perpendicular Media – New PMR media requires a specific field and leakage shape to guarantee proper conditioning without residual noise.

Longitudinal Media – LMR  media requires a specific field and leakage shape to guarantee proper conditioning without residual noise.

Our experience with designing single disk erasers for this media type guarantees a quick turn around from concept to functional device.

When working with our engineering group, you might be asked:

  1.  What type of media is being erased?
    a. LMR
    b. PMR

2.   What erase field magnitude is required?

3.   What size media is being erased?

4.   What are the physical size constraints for the device?


  1. Copper Wire (insulation application dependent)

Permanent Magnets

  1. NdFeB – Highest Strength/volume, moderate cost., moderate temperature extremes (150°C),
  2. SmCo – High Strength/volume, highest cost, high temperature extremes (300°C)
  3. Ceramic – Low Strength/volume, lowest cost, high temperature extremes (300°C)
  4. Alnico – Moderate to High Strength/volume, high cost, highest temperature extremes (450°)

Frame Materials

  1. Nickel Plated  Carbon Steels (1010, 1045) – high saturation flux, low cost, poor corrosion resistance
  2. Martensitic Stainliess Steels (416, 430) – moderate-high saturation flux, moderate cost, good corrosion resistance
  3. Nickel Super Alloys (Hiperco®) – highest saturation flux, highest cost, excellent corrosion resistance
  4. Nickel Plated Aluminum – low cost, light weight
  1. Have these devices been supplied to industry already?
  2. What types of field levels are achievable?
  1. We have designed and manufactured devices for both PMR and LMR media that are successfully operating in production environments today.
  2. This is dependent on the physical size available for the device as well as gap requirements.  In general, however, these devices can be designed to produce fields upwards of 1T on the media surface.

We do not offer a “standard” eraser magnet as each application requires a fair amount of customization in order to assure proper functionality.  Based on the input from the customer (size, environment, magnetic field specifics), the design is evaluated for feasibility to determine if further engineering efforts are warranted.  Typically, the feasibility study is used to determine if the proposed magnetic field magnitude across the substrate is achievable. 

Tuning the magnetic field to achieve alignment, skew angles, and leakage forms is an engineering intensive effort which requires an iterative finite element analysis and can usually be completed within 1-2 weeks upon initiation.

Once a design is agreed upon, a prototype can typically be produced within 8-10 weeks, but this depends upon material availability.