Advanced Materials: TechConnect Briefs 2015Advanced Materials TechConnect Briefs 2015

Nanoscale Materials Characterization Chapter 1

First-Order-Reversal-Curve Analysis of Nano-composite Permanent Magnets

B.C. Dodrill
Lake Shore Cryotronics, United States

pp. 63 - 66

Keywords: first-order-reversal-curves, nano-composite mermanent magnets, magnetization analysis

Rare-earth and ferrite permanent magnet materials are indispensable elements in many electronic devices such as electrical motors, hybrid vehicles, portable communications devices, speakers, sensors, etc. Owing to the decreased availability of, and increasing cost of rare-earth elements, significant research is underway to develop strong permanent magnet materials that do not rely as heavily on rare-earth constituents, e.g., nano-composite exchange spring magnets comprised of a hard high coercivity phase, exchange coupled to a soft high saturation magnetization phase, which increases the energy density and decreases the cost of the magnet because less hard phase material is needed; multi-phase composite nanostructures such as soft shell/hard core magnetic nanowires; hybrid magnets, etc. The magnetic characterization of such materials is usually made by measuring a hysteresis loop, however it is very difficult to unravel the complex magnetic signatures of multiphase materials, and obtain information of interactions or coercivity distributions, from the hysteresis loop alone. First-order-reversal-curves (FORC) provide a means for determining the distribution of interaction fields between magnetic particles, and for distinguishing between magnetic phases in composite materials that contain more than one magnetic phase. In this paper we will discuss the FORC technique, and present results for various multiphase nano-composite magnets.