Magnetic Characteristics of Quaternary SmMn2Ge2-BASED Materials with Magnetic Layered Structure

Intrinsic magnetic properties of quaternary Sm_1-xR_xMn₂Ge₂ 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 Sm_1-xGd_xMn₂Ge₂ 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.