First-order-reversal-curve analysis of magnetic multilayer films and permanent magnet materials

3D FORC diagram of an exchange bias thin film
3D FORC diagram of an exchange bias thin film

In past blog entries, we discussed the value of first-order-reversal-curve (FORC) analysis when characterizing magnetic interactions in nickel (Ni) nanowires and rocks. Now, we’re looking at how FORCs are beneficial for analyzing:

  • Exchange bias phenomena in magnetic multilayer films, which are commonly used as read heads in high-density recording media. For more on this, read our latest application note. In it, we present results for two (FeNi/IrMn)n magnetic multilayer films where (n) is the number of layer repetitions. We show how FORC analysis is used to correlate exchange bias with in-homogeneities existing at the anti-ferromagnetic (AFM)/ferromagnetic (FM) interface.
  • Permanent magnet materials, which are heavily used in many electronic devices, such as electrical motors, hybrid vehicles, and portable communications devices. In this application note, we present FORC measurement results for three permanent magnet samples: SmCo nanoparticles, AlNiCo, and a hybrid sample consisting of a mixture of soft (ferrite) and hard (SmCo) phases. We show that FORC analysis can be used to differentiate between soft and hard phases in hybrid systems.

In both application notes, a Lake Shore PMC MicroMag™ 3900 Series VSM was used to characterize the magnetic interactions and coercivity distributions in these materials via FORC analysis. The 3900 Series system, as well as our PMC MicroMag™ 2900 Series AGM, is particularly fast at measuring FORCs. A sequence of FORCs can contain thousands of data points which can be unwieldy and cumbersome if the measurement is inherently slow; therefore, measurement speed is very important. The Lake Shore PMC MicroMag™ VSM and AGM systems are arguably the standard for FORC measurements because of their measurement speed.

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