Berlin 2018 – scientific programme

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MA: Fachverband Magnetismus

MA 50: Soft and hard permanent magnets

MA 50.6: Talk

Thursday, March 15, 2018, 16:15–16:30, EB 301

Using FORC to understand the microstructure-micromagnetism relationship in supermagnets — •Sven Erik Ilse, Felix Groß, Joachim Gräfe, and Eberhard Goering — Max Planck Institute for Intelligent Systems, Germany

First-order-reversal-curve (FORC) diagrams yield a great variety of magnetic information such as coercive and interaction field distributions. We have recently demonstrated that FORC on MnBi can provide deep insight in the relationship between magnetism and microstructural properties, as grain size distributions and grain shapes[1]. Following these studies we investigated neodymium based permanent magnets and their FORC density relationship to microstructural properties. We systematically manipulated the microstructure of the samples by consecutive annealing (at different temperatures and intervals), and correlated their grain size-distributions with FORC diagrams. Our analysis of the grain size distributions showed that the grain sizes shift to higher diameters and the distribution broadens for longer annealing times. The room temperature FORC diagrams revealed that the width of the coercive field distribution increases. Correlating the widths of grain size- and coercive field- distributions reveals a linear dependence, which enables us to draw conclusions about grain sizes directly from FORC measurements. Our results demonstrate the versatility of FORC investigations providing rich additional information and enabling detailed understanding of coercive and interaction field distributions of our samples related to microstructure and grain size distributions.

[1] S. Muralidhar, et al., Physical Review B 95.2 (2017): 024413.