The structure, magnetic properties, magnetotransport and temperature coefficient of resistivity of hexagonal 4H-SrMnO3 manganite

The perovskite hexagonal SrMnO ₃ manganite with four layers (4H-SrMnO ₃) have been one of the hot topics in materials science due to the physical characteristics of antiferromagnetic, ferroelectric, and thermoelectric effects. The transport properties and magnetoresistance (MR) effect of 4H-SrMnO ₃ have seldom been reported. The structure, temperature coefficient of resistivity (TCR), magnetic and magnetotransport properties of the 4H-SrMnO ₃ SrMnO ₃ manganite obtained by solid state reaction have been investigated in this work. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements at room temperature reveal that the SrMnO ₃ sample exhibits a pure hexagonal symmetric structure, with uniform distribution of particles and elements. Under applied magnetic fields of 2000 Oe, the SrMnO ₃ sample exhibits a transition from antiferromagnetic (AFM) to paramagnetic (PM) behavior at approximately 280 K, known as the Néel temperature (T _N). The resistance is influenced by the magnetic field, but overall exhibits an insulating state. Remarkably, the SrMnO ₃ sample shows significant MR effect near room temperature. The negative MR near room temperature varies from 5.8 % with 1 T field to 16.8 % with 6 T field, indicating an existence of obvious MR in the hexagonal AFM SrMnO ₃ manganite. Furthermore, the maxmium value of TCR reaches 4.34 % K ⁻¹ near room temperature. These findings of room-temperature TCR and room-temperature MR in the AFM 4H-SrMnO ₃ hold immense value for the research and potential application of the AFM spintronics and devices.