Dresden 2017 – scientific programme
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MA: Fachverband Magnetismus
MA 56: Bulk Materials: Soft and hard permanent magnets
MA 56.10: Talk
Thursday, March 23, 2017, 17:30–17:45, HSZ 403
Magnetization behavior of hexagonal ferrites observed by in-situ Magnetic Force Microscopy — •Tim Helbig1, Fabian Rhein2, Volker Neu3, Michael Krispin2, and Oliver Gutfleisch1 — 1TU Darmstadt — 2Siemens AG — 3IFW Dresden
The sintering temperature of hexagonal ferrites with increasing partial Al substitution was systematically varied to obtain different microstructures. The grain size was found to range from a few hundred nanometers to several hundred micrometers. The grain size distribution depended on the Al content as well as the pre-milling and sintering conditions. Magnetic Force Microscopy (MFM) showed that the microstructure consists of a mixture of grains below the critical single-domain size, and larger grains with a multi-domain structure in the thermally demagnetized state (TDS). An in-situ MFM study was carried out depicting the magnetization from the TDS as well as the demagnetization under external magnetic field. From the surface domain contrast a magnetization was derived which quantitatively matches the global i.e. bulk magnetization obtained by SQUID magnetometry. The shape of the initial magnetization curve and the magnetization from the DC demagnetized state was correlated with the in-situ MFM data revealing a distinctly different magnetization behavior depending on grain size. Financial support by the German federal state of Hessen through its LOEWE program "RESPONSE" is gratefully acknowledged. The material development has been performed in BMBF funded project KomMa (03X3582).