Competitive Advantages of Shb Magnetic Measurement Systems

"Competing" Systems

1. Vibrating Sample Magnetometer (VSM)

   VSM’s can make the basic BH loop measurements (Bs, Hc), and some have probes to measure R and dR. They operate by applying a slowly changing DC field to the sample (via a large magnet with concentrating pole pieces), and plotting the BH loop as the DC field slowly changes.

   Limitations:

   • They work only on very small pieces of a wafer, or specially made small diameter wafers, while the SHB instruments can measure whole wafers up to 8" (200 mm) in diameter.
   • A loop can take up to several minutes to trace out, while the SHB instruments are "real-time", displaying 10 loops per second. Therefore measurements take much longer to complete.
   • The signal-to-noise ratio and therefore the measurement repeatability is inferior to a looper when measuring thin materials.
   • There is no easy way to get the critical rotational orientation of a sample exactly correct, while on an SHB instrument the operator rotates the sample and watches the loop change in real time.
   • They have limited accuracy at low field strengths (low Hc values) due to remanent magnetization of their pole pieces. The SHB instruments operate at AC, and have no such limitation.
   • They cannot measure magnetostriction at all.
   • Limited R and dR (magnetoresistance) capability

   Advantages:

   • Capable of generating very high field strengths (10,000 Oersteds or more), which is necessary to measure the materials used for hard drive platters, as well as some componenets of advanced (GMR) head designs. The SHB Model 109A was limited to 200 Oersteds, but the new high-field 1" coil assembly allows generation of 1000 Oe fields for 1" diameter wafers. The new SHB Model 110 instrument can generate 10,000 Oersteds or higher fields, and retains all of the other operating advantage of the AC meaurement system used in the 109A.

2. LaFouda Automated Magnetostriction Measurement System

   This is a specialized instrument that measures only magnetostriction.

   Limitations:

   • Cannot measure an entire wafer — requires a small strip to be cut.
   • Measures only magnetostriction, yet costs as much as a full SHB system

   Advantages:

   • Better resolution than the SHB systems…but not by much. SHB has co-authored a published paper that describes a measurement technique that allows the current SHB system to achieve essentially the same resolution as the LaFouda.. And the new SHB magnetostriction pickups due out next year should be as good or better than a LaFouda system, without advanced measurement techniques being needed.

3. Dedicated 4-point probing systems

   (made by one or more manufacturers)

   Limitations:

   • Measure only resistance and magnetoresistance, not basic BH loop parameters or magnetostriction.

   Advantages:

   • More flexibility in probe arrangement and orientation, as well as allowing for sophisticated measurements of GMR effect versus angle. The new 109-66C pickup from SHB, along with our latest software, provide all of this flexibility in probing and measurement.