Magnetic study of SmCoAsO showing a ferromagnetic-antiferromagnetic transition

Abstract

We synthesized a polycrystalline sample of SmCoAsO and measured its magnetization (M) at various of temperatures (T) and magnetic fields (H). As decreasing T, a paramagnetic to ferromagnetic transition occurs at 70 K, and then a ferromagnetic to antiferromagnetic transition occurs at 42 K. In the antiferromagnetic phase, we observed the behavior characteristic of metamagnetic transitions in M-H curves. From the results of magnetization measurements up to H=56 T, we successfully draw the magnetic phase diagram of SmCoAsO. We observed convex behavior in Arrott plots in the ferromagnetic temperature region as seen in MnSi, Fe1−xCoxSi, and isostructural compound LaCoAsO. We discussed the magnetic property of SmCoAsO above TC based on the spin-fluctuation theory.