Magnetic property of Al-Mg alloys and intermetallic compounds

Highlights: • Abnormally enhanced paramagnetism observed for Al₁₂Mg₁₇ and Al₄₄Mg₅₆ compounds, while diamagnetism for Al₄₅Mg₅₅. • The substitution of either element for the host produced diamagnetic contributions to the magnetization. • DFT calculations could not explain observed drastic variations of the magnetization of Al-Mg compounds. -- Abstract: Magnetization (M) of binary Al-Mg alloys and intermetallic compounds were measured in the temperature (T) range from 10 to 300 K. The Al-rich alloys Al - 2, 3, 4, 5, and 10 at% Mg) revealed diamagnetic contributions to the magnetization correlating to the Mg concentrations. For the β-phase Al₃Mg₂ the M vs T curve lay very close to that of pure Mg over the entire measured T region. The magnetization of the γ-phase samples exhibited enhanced paramagnetism for Al₄₄Mg₅₆ and Al₁₂Mg₁₇, but the diamagnetism for Al₄₅Mg₅₅. There were diamagnetic contributions to the magnetization of the Mg-rich alloys (Mg - 5, 10, and 15 at% Al) depending on the Al concentration, possibly due to the γ-phase precipitations. Heat capacity of the γ-phase samples and pure Al were measured to estimate the electronic specific heat coefficients which were found to be almost the same. Density functional theory calculations for the Al-Mg compounds were carried out to aid interpretation of the observed magnetization.