Conductivity and incommensurate antiferromagnetism of Fe _1.02Se _0.10Te _0.90 under pressure

By performing resistivity, bulk susceptibility and neutron diffraction on single crystals of Fe _1.02Se _0.10Te _0.90 under pressure, we show that an external pressure can enhance both conductivity and magnetism simultaneously. Surprisingly, the pressure-induced magnetic order is nearly three-dimensional, and incommensurate along both the c-axis and the a-axis, which is accompanied by a structural phase separation. Our powder neutron diffraction data show that the Fe(Se, Te) ₄ tetrahedron becomes more regular under pressure, which is consistent with the enhancement of the metallicity but is counterintuitive to the three-dimensional magnetic order.