Magnetic characteristics of quaternary SmMn2Ge2-based materials with magnetic layered structure

Intrinsic magnetic properties of quaternary Sm1-xRxMn2Ge2 compounds with R = Y, x = 0.25 and R = Gd, x = 0.25, 0.5, and 0.6 have been studied at temperatures ranging 4.2 K to 350 K and in applied field strengths up to 60 kOe. Partial substitution of Sm by Gd or Y atoms raises the transition temperature T-AFM/FM Of antiferromagnetic (AFM) to ferromagnetic phase (FM) to vicinity of room temperature. A magnetic phase diagram for Sm1-xGdxMn2Ge2 as a function of Gd concentration has been determined. It was found that replacement of 50% Sm by Gd atoms resulted in an increase of temperature region of the AFM Phase by about 105 K. This result may indicate enhancement in the strength of the antiferromagnetic coupling of the Mn-Mn sublattices.