Regensburg 2013 – scientific programme
Parts | Days | Selection | Search | Updates | Downloads | Help
MA: Fachverband Magnetismus
MA 14: Micromagetic Simulation and Electron Theory of Magnetism
MA 14.2: Talk
Tuesday, March 12, 2013, 09:45–10:00, H23
Micromagnetic analysis of nucleation and pinning processes in the intermetallic compound MnBi — Dagmar Goll1 and •Helmut Kronmüller2 — 1Aalen University, Materials Research Institute, Aalen — 2Max-Planck-Institute for Intelligent Systems, Stuttgart
The low temperature phase (LTP) of the binary intermetallic compound MnBi shows extraordinary magnetic properties in the temperature range up to 600 K. An anisotropy constant of 2.2 MJ/m3 at 400 K and a large magnetic moment of 3.6 Bohr magnetons of Mn atoms predestinates the low temperature phase (LTP) of MnBi as a high temperature permanent magnet. Depending on the type of microstructure the hysteresis loops are governed either by nucleation or domain wall pinning processes. A micromagnetic analysis of the temperature dependence and of the angular dependence of the coercive field allows a decision whether the nucleation or the pinning mechanism governs the hysteresis loop. In the case of the intermetallic compound MnBi and other supermagnets in general the Stoner-Wohlfarth-Theory has to be expanded with respect to higher anisotropy constants and microstructural effects, as misaligned grains, and the role of grain surfaces with reduced anisotropy constants. Taking care of these effects leads to a quantitative interpretation of recent experimental results obtained for nanocrystalline magnets [1]. Nucleation hardened nanocrystalline magnets with coercive fields up to 2.5 Tesla at 500 K are found to be superior to the pinning hardened multiphase magnets of MnBi. [1] J.B. Yang et al., Appl. Phys. Letters 99, 062505 (2011).