Critical behavior in the ferromagnet

Abstract

High-Curie-temperature ferromagnets are promising candidates for designing new spintronic devices. Here we have successfully synthesized the single crystal of the itinerant ferromagnet Mn5Ge3 using flux method. Its critical properties were investigated by means of bulk dc-magnetization at the boundary of the paramagnetic (PM) and ferromagnetic (FM) phase to determine intrinsic magnetic interactions. 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 acquired 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 interaction in Mn5Ge3 exhibits three-dimensional Ising-like behavior. The magnetic exchange interaction is found to decay as J(r) r-4.855, meaning that the spin interactions exceed the nearest neighbors, which may be related to the different Mn–Mn interactions with inequal exchange strengths.