Growth and characterization of the magnetic topological insulator candidate Mn$_2$Sb$_2$Te$_5$

Abstract: We report a new member of topological insulator (TI) family i.e., Mn$_2$Sb$_2$Te$_5$, which belongs to MnSb$_2$Te$_4$ family and is a sister compound of Mn$_2$Bi$_2$Te$_5$. An antiferromagnetic layer of (MnTe)$_2$ has been inserted between quintuple layers of Sb$_2$Te$_3$. The crystal structure and chemical composition of as grown Mn$_2$Sb$_2$Te$_5$ crystal is experimentally visualized by single crystal XRD (SCXRD) and field emission scanning electron microscopy (FESEM). The valence states of individual constituents i.e., Mn, Sb and Te are ascertained through X ray photo electron spectroscopy (XPS). Different vibrational modes of Mn$_2$Sb$_2$Te$_5$ are elucidated through Raman spectroscopy. Temperature-dependent resistivity of Mn$_2$Sb$_2$Te$_5$ resulted in metallic behaviour of the same with an up-turn at below around 20K. Further, the magneto-transport R(T) vs H of the same exhibited negative magneto-resistance (MR) at low temperatures below 20K and small positive at higher temperatures. The low Temperature -ve MR starts decreasing at higher fields. The magnetic moment as a function of temperature at 100Oe and 1kOe showed AFM like down turn cusps at around 20K and 10K. The isothermal magnetization (MH) showed AFM like loops with some embedded FM/PM domains at 5K and purely paramagnetic (PM) like at 100K. The studied Mn$_2$Sb$_2$Te$_5$ clearly exhibited the characteristics of a magnetic TI (MTI).