Temperature evolution of Fe–27Ga structure: comparison of in situ X-ray and neutron diffraction studies

Comparative in situ X-ray and neutron diffraction studies of the phase transitions in a high magnetostriction Fe–27Ga alloy sample have been performed, with heating up to 850°C and subsequent cooling to room temperature. Different structural information (phase content, phase-transition temperatures, unit-cell behaviour) is obtained for the bulk sample and its surface, and this fact is discussed here in terms of the difference between the scattering properties of X-rays and neutrons. In particular, a gallium-deficient phase with A2-type structure was found on the surface of the sample. The results demonstrate that conventional X-ray diffraction methods are insufficient for precise structural analysis of bulk samples of galfenols and cannot be used alone to build their phase diagrams.