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Direct Observation of Reverse Magnetic Domain and Magnetic DomainWall Motion in Nd-Fe-B Magnet at High Temperature by LorentzMicroscop

Published online by Cambridge University Press:  14 January 2016

Toshimasa Suzuki ,
Koichi Kawahara ,
Masaya Suzuki ,
Kenta Takagi  and
Kimihiro Ozaki
Toshimasa Suzuki*
Affiliation:
Materials Research and Development Laboratory, Japan Fine Ceramics Center (JFCC), Nagoya, 456-8587, Japan.
Koichi Kawahara
Affiliation:
Materials Research and Development Laboratory, Japan Fine Ceramics Center (JFCC), Nagoya, 456-8587, Japan.
Masaya Suzuki
Affiliation:
Materials Research and Development Laboratory, Japan Fine Ceramics Center (JFCC), Nagoya, 456-8587, Japan.
Kenta Takagi
Affiliation:
Inorganic Functional Materials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, 463-8560, Japan.
Kimihiro Ozaki
Affiliation:
Inorganic Functional Materials Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, 463-8560, Japan.
*
*(Email: [email protected])
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Abstract

We conducted the in-situ observations of the magnetic domain structure change inNd-Fe-B magnets at high temperature by transmission electron microscopy (TEM) /Lorentz microscopy with applying an external magnetic field. Prior toobservation, a thin foil was magnetized by an external magnetic field of 2.0 Tto almost saturation, then the magnetic domain structures were observed by theFresnel mode with in-situ heating. At 225°C, reverse magnetic domainswere found to generate in the thin foil sample without applying an externalmagnetic field. When we applied a magnetic field on the same direction to thepre-magnetization direction at 225°C, one magnetic domain wall waspinned by a grain boundary and the other magnetic domain wall moved. As theresults, the reverse magnetic domain shrank then annihilated. When we cut theapplied magnetic field, the reverse magnetic domain generated at almost the samelocation. On the other hand, when we applied a magnetic field to the foils inthe opposite direction, the reverse domain started to grow, i.e., magneticdomain walls started to move. The observation results of the shrink or growth ofthe reverse domain showed that the pinning effect of grain boundary againstdomain wall motion would be different depending on the applied magnetic fielddirection. Moreover, domain walls was observed to be pinned by grain boundariesat elevated temperature, so that the coercivity of Nd-Fe-B magnet would occur bypinning mechanism.

Keywords

transmission electron microscopy (TEM)magnetic propertiesmicrostructure
Type
Articles
Information
MRS Advances , Volume 1 , Issue 3: Nanomaterials and Synthesis , 2016 , pp. 241 - 246
Copyright
Copyright © Materials Research Society 2016 

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References

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