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 Mn${}_5$Ge${}_3$ 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 $\beta =0.336\pm 0.001$ with a critical temperature $T_c=300.29\pm 0.01$ K and $\gamma =1.193\pm 0.003$ with $T_c=300.15\pm 0.05$ K are obtained by the modified Arrott plot, whereas $\delta =4.61\pm 0.03$ is deduced by a critical isotherm analysis at $T_c=300$ 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 Mn${}_5$Ge${}_3$ exhibits three-dimensional Ising-like behavior. The magnetic exchange is found to decay as $J(r)\approx r^{-4.855}$ 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 Mn${}_5$Ge${}_3$ results in a small deviation of obtained critical exponents from those for standard 3D-Ising model.

8 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1803.05905 by other authors