Low-Dimensional Magnetic Semimetal Cr0.65Al1.35Se3

While exploring novel magnetic semiconductors, the new phase Cr 0.65 Al 1.35 Se 3 was discovered and characterized by both structural and physical properties. Cr 0.65 Al 1.35 Se 3 was found to crystallize into orthorhombic CrGeTe 3 -type structure with space group Pnma (no. 62). Vacancies and mixed occupancies were tested, and the results show that one of the 4 c sites accommodates a mixture of Cr and Al atoms, while the other 4 c site is fully occupied by Al atoms. Unique structural features include a T-shaped channel network created from the edge-sharing Cr/Al@Se 6 and Al@Se 4 polyhedra and a zipper effect of the puckered Se atoms inside the columnar channels. The round peak observed in the temperature-dependent magnetic susceptibility (χ g ) plot at ∼8(1) K corresponds to the antiferromagnetic-type transition in Cr 0.65 Al 1.35 Se 3 . However, the positive θ CW indicates an additional ferromagnetic interaction, which is highly likely due to the complex magnetic structure arising from the mixed Cr/Al occupancies on the 4 c site. Electrical resistivity measurements confirm that Cr 0.65 Al 1.35 Se 3 is a semimetal with a positive magnetoresistance. Here we present the characterization and determination of the crystal structure and physical properties for this new material.