Correlation of ferromagnetism and structure in Fe observed by high resolution X-ray diffraction

In order to find evidence of the ferromagnetic interaction, the crystal structure and the magnetic property of pure Fe are investigated from room temperature to 950 °C by measuring X-ray diffraction patterns and magnetizations. The ferro–paramagnetic transition occurs near 770 °C with large stretch and contraction of lattice constants, which is an evidence of correlation of ferromagnetism and crystal structure. The structural phase transition between α-bcc and γ-fcc is observed above 850 °C. The d-spaces between (011) and (101) planes, observed with a high resolution triple-axis X-ray diffractometer, differ at RT; Δd≡d₁₀₁–d₀₁₁≈0.45%. The structure of Fe is pseudocubic, showing a body-centered tetragonal structure of c/a<1 generated by magnetostriction (exchange striction) induced by spontaneous magnetization.