Magnetic phase transitions in Y 1−x Tb x Mn 6 Sn 6 , La 1−x Sm x Mn 2 Si 2 , Lu 2 (Fe 1−х Mn x ) 17 , and La(Fe 0.88 Si x Al 0.12−x ) 13 intermetallic compounds

Abstract Magnetic properties have been measured for the Y1−xTbxMn6Sn6, La1−xSmxMn2Si2, Lu2(Fe1−хMnx)17, and La(Fe0.88SixAl0.12–x)13 systems which show up transitions from antiferromagnetic to ferromagnetic state upon changing concentration of the constituents or application of magnetic field. We determined the concentrations and temperatures of the magnetic phase transitions and plotted magnetic phase diagrams. Near a critical concentration, the AF–F transition can be realized in low magnetic fields, which makes these compounds attractive for magnetothermal applications. Using the data of the magnetization measurement, we determined the isothermal magnetic entropy change in a wide temperature range. All the studied systems have a layered magnetic structure with the positive intralayer exchange interaction and the interlayer exchange integrals of different signs depending on the composition and temperature. For the compounds La(Fe0.88SixAl0.12−x)13 with the cubic crystal structure, the origin of formation of a layered magnetic structure is discussed based on the data of Mossbauer studies which revealed a difference in the local surrounding of resonant atoms in the compounds with different magnetic orders.