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Abstract

The magnetic, thermal, and transport properties as well as electronic band structure of MnPtSi are reported. MnPtSi is a metal that undergoes a ferromagnetic transition at T-c = 340(1) K and a spin-reorientation transition at T-N = 326(1) K to an antiferromagnetic phase. First-principles electronic structure calculations indicate a not-fully polarized spin state of Mn in a d(5) electron configuration with J = S = 3/2, in agreement with the saturation magnetization of 3 mu(B) in the ordered state and the observed paramagnetic effective moment. A sizable anomalous Hall effect in the antiferromagnetic phase alongside the computational study suggests that the antiferromagnetic structure is noncollinear. Based on thermodynamic and resistivity data we construct a magnetic phase diagram. Magnetization curves M(H) at low temperatures reveal a metamagnetic transition of spin-flop type. The spin-flopped phase terminates at a critical point with T-cr approximate to 300 K and H-cr approximate to 10 kOe, near which a peak of the magnetocaloric entropy change is observed. Using Arrott plot analysis and magnetoresistivity data we argue that the metamagnetic transition is of a first-order type, whereas the strong field dependence of T-N and the linear relationship of the T-N with M-2 hint at its magnetoelastic nature.