Engineering the atomic structure of an inorganic semiconductor to create isolated one-dimensional magnetic subunits that are embedded within the semiconducting crystal lattice can enable chemical and electronic manipulation of magnetic ordering within the magnetic domains, paving the way for (1) the investigation of new physical phenomena such as the interactions between electron transport and localized magnetic moments at the atomic scale and (2) the design and fabrication of geometrically frustrated magnetic materials featuring cooperative long-range ordering with large magnetic moments. We will discuss the design, synthesis, crystal structure and magnetic behavior of (MnxPb2-x)Pb2Sb4Se10, a family of three-dimensional (3D) manganese-bearing main-group metal selenides featuring quasi isolated [(MnxPb2-x)3Se30]8 hexanuclear magnetic ladders coherently embedded and uniformly distributed within a purely inorganic semiconducting framework, [Pb2Sb4Se10]. Careful structural analysis of the magnetic subunit, [(MnxPb2-x)3Se30]8 and the temperature dependent magnetic susceptibility of (MnxPb2-x)Pb2Sb4Se10, indicate that the compounds are geometrically frustrated one-dimensional (1D) ferromagnets. Interestingly, the degree of geometrical spin frustration (f) within the magnetic ladders and the strength of the intra-chain anti-ferromagnetic (AFM) interactions strongly depend on concentration (x value) and the distribution of the Mn atom within the magnetic substructure. The combination of strong intra-chain AFM interactions and geometrical spin frustration in the [(MnxPb2-x)3Se30]8 ladders results in a cooperative ferromagnetic order with exceptionally high magnetic moment at around 125K. Magnetotransport study of the Mn2Pb2Sb4Se10 composition over the temperature range from 100 to 200 K revealed negative magnetoresistance (NMR) values and also suggested a strong contribution of magnetic polarons to the observed large effective magnetic moments.

Geometrical spin frustration and ferromagnetic ordering in (MnxPb2-x)Pb2Sb4Se10

247th National Meeting (2014)

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