Materials Transactions Online

Materials Transactions, Vol.46 No.08 (2005) pp.1764-1767
© 2005 The Japan Institute of Metals

In Situ TEM Observation of Thermally-Induced First-Order Magnetic Transition in Itinerant-Electron Metamagnetic La(FexSi1-x)13 Compounds

Naoyuki Kawamoto1,, Yasukazu Murakami1, Daisuke Shindo1, Shun Fujieda2, Asaya Fujita2 and Kazuaki Fukamichi2

1Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan
2Department of Material Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan

Defocus mode of Lorentz microscopy has revealed change in the magnetic microstructure with a first-order magnetic phase transition in La(FexSi1-x)13 compounds (0.86 ≤q x ≤q 0.90). Upon heating specimens from the ferromagnetic phase to the paramagnetic phase, magnetic domains disappear instantaneously at the Curie temperature, concurrent with a substantial change in the volume. The observations are consistent with the feature of the first-order phase transition, which gives rise to extraordinary phenomena of these compounds such as large magnetocaloric effects.

(Received 2005/4/25; Accepted 2005/6/17; Published 2005/8/15)

Keywords: itinerant-electron metamagnetic transition, Lorentz microscopy, transmission electron microscopy, first-order transition, magnetic domain, magnetocaloric effect, magnetovolume effect

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