Abstract
Magnetic properties of the La1-xGdxMn2Si2 (0 ≤ x ≤ 1) compounds with layered ThCr2Si2-type structure have been studied using quasi-single-crystalline and polycrystalline samples. Concentration dependences of critical temperatures of magnetic phase transitions, effective magnetic moments and paramagnetic Curie temperatures have been determined for different compositions. Using the obtained results, we plotted the concentration magnetic phase diagram. The type of the interlayer Mn-Mn magnetic ordering is found to depend on the intralayer Mn-Mn distance. With increasing the Gd concentration, the ordering of the Mn sublattice changes from ferromagnetic (F) to antiferromagnetic (AF) at x ≈ 0.2–0.27. We found that the concentration F-AF magnetic phase transition is accompanied by a change of magnetic anisotropy from the easy-axis to the easy-plane type at low temperatures when the Gd moments are magnetically ordered. The transition can hardly be expected since the Mn sublattice has a strong easy-axis type anisotropy in LaMn2Si2, while the Gd has zero orbital momentum and typically weakly contribute to the magnetic anisotropy. The spin reorientation in the La1-xGdxMn2Si2 has been attributed to a competition between the Gd-Mn and Mn-Mn exchange interactions.
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