Critical behavior in the Mn$_{5}$Ge$_{3}$ ferromagnet

Abstract

High-Curie-temperature ferromagnets are promising candidates for designing new spintronic devices. Here we have successfully synthesized a single-crystal sample of the itinerant ferromagnet Mn5Ge3 used flux method and its critical properties were investigated by means of bulk dc-magnetization at the boundary between the ferromagnetic (FM) and paramagnetic (PM) phase. Critical exponents β = 0.336 ± 0.001 with a critical temperature Tc = 300.29 ± 0.01 K and γ = 1.193 ± 0.003 with Tc = 300.15 ± 0.05 K are obtained by the modified Arrott plot, whereas δ = 4.61 ± 0.03 is deduced by a critical isotherm analysis at Tc = 300 K. The self-consistency and reliability of these critical exponents are verified by the Widom scaling law and the scaling equations. Further analysis reveals that the spin coupling in Mn5Ge3 exhibits three-dimensional Ising-like behavior. The magnetic exchange is found to decay as J(r) ≈ r −4.855 and the spin interactions are extended beyond the nearest neighbors, which may be related to different set of Mn-Mn interactions with unequal magnitude of exchange strengths. Additionally, the existence of noncollinear spin configurations in Mn5Ge3 results in a small deviation of obtained critical exponents from those for standard 3D-Ising model.