High Curie temperature ferromagnetic structures of (Sb(2)Te(3))(1−x)(MnSb(2)Te(4))(x) with x = 0.7–0.8

Magnetic topological materials are promising for realizing novel quantum physical phenomena. Among these, bulk Mn-rich MnSb(2)Te(4) is ferromagnetic due to Mn(Sb) antisites and has relatively high Curie temperatures (T(C)), which is attractive for technological applications. We have previously reported the growth of materials with the formula (Sb(2)Te(3))(1−x)(MnSb(2)Te(4))(x), where x varies between 0 and 1. Here we report on their magnetic and transport properties. We show that the samples are divided into three groups based on the value of x (or the percent septuple layers within the crystals) and their corresponding T(C) values. Samples that contain x < 0.7 or x > 0.9 have a single T(C) value of 15–20 K and 20–30 K, respectively, while samples with 0.7 < x < 0.8 exhibit two T(C) values, one (T(C1)) at ~ 25 K and the second (T(C2)) reaching values above 80 K, almost twice as high as any reported value to date for these types of materials. Structural analysis shows that samples with 0.7 < x < 0.8 have large regions of only SLs, while other regions have isolated QLs embedded within the SL lattice. We propose that the SL regions give rise to a T(C1) of ~ 20 to 30 K, and regions with isolated QLs are responsible for the higher T(C2) values. Our results have important implications for the design of magnetic topological materials having enhanced properties.