In Situ TEM Observation of Thermally-Induced First-Order Magnetic Transition in Itinerant-Electron Metamagnetic La(Fe_xSi_1−x)₁₃ Compounds

Abstract

Defocus mode of Lorentz microscopy has revealed change in the magnetic microstructure with a first-order magnetic phase transition in La(Fe_xSi_1−x)₁₃ compounds (0.86≤x≤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.