Placing spins in semiconductors

Non-technical summary

The remarkable optical and electronic properties of metal-halide semiconductors, which adopt the perovskite crystal structure, make them excellent candidates as component materials in solar cells and light emitting devices (e.g., LEDs). Perovskites that excel in these applications, however, are nonmagnetic. Thus, metal-halides with excellent optical and electronic properties and a high density of magnetic spins remain essentially unknown.

With this project, supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials programs in the Division of Materials Research, Professor Hema Karunadasa and her research group at Stanford University propose the design and synthesis of new magnetic semiconductors that form in solution. These materials, composed primarily of metal ions and halides, are expected to display new phenomena stemming from interactions between a) the spins of magnetic ions and b) the spins and conducting electrons.

The new materials designed in this project could have strong applications in the field of spintronics, where magnetic spins add an additional degree of control over electronic devices, has great potential in next-generation high-speed and low-power information technologies. Revealing such properties in materials that can be deposited from solution as films could dramatically cut costs of such applications.

Further, new phenomena of fundamental scientific interest may be realized in these materials, including a) magnetic spins that cannot order, even at very low temperatures, leading to exotic spin patterns, b) spins that align to create permanent magnets, and c) magnetic spins that control the flow of electrons inside a material. Local high-school students will participate in the research through summer programs and the PI will continue redesigning general chemistry to introduce undergraduate students to materials chemistry earlier in the curriculum.

Through a collaboration with Hampton University, Virginia, materials developed in this project will be assessed for near- and mid-IR emission. Undergraduates at Hampton University and Stanford University will learn how to control light through the incorporation of magnetic impurities in metal-halides.

Technical summary

The remarkable optoelectronic properties of halide perovskites have rendered them excellent candidates for photovoltaic and phosphor applications. The common perovskites explored for these applications, however, are nonmagnetic. Thus, metal-halides that possess comparable optoelectronic properties and contain a high density of spins remain essentially unknown.

Spintronics has great potential in next-generation high-speed and low-power information technologies, for example, magnetoresistance has applications in high-density data storage. Revealing such phenomena in materials that can be deposited from solution as films could dramatically cut costs of such applications. This project, supported by the Solid State and Materials Chemistry and Electronic and Photonic Materials programs in the Division of Materials Research, is addressing this challenge by developing new synthetic routes toward the self-assembly of magnetic semiconductors in solution.

These new materials are anticipated to display unprecedented phenomena in metal-halides, derived from spin-spin and spin-carrier interactions. Specific objectives of the proposed work are: 1) the design of new metal-halide architectures that contain spins in the organic or inorganic components, 2) the development of magnetic metal-halides with dispersive electronic bands and tunable carrier concentrations, 3) the characterization of magnetic, charge transport, and optoelectronic properties of these new materials.

Fundamentally new phenomena in metal-halides will also be targeted, including magnetic frustration, spin polarization, and coupling between itinerant electrons and an embedded magnetic sublattice. High-school students will participate in summer research programs and the PI will continue to redesign freshman chemistry to introduce students to materials chemistry earlier in the curriculum.

Through collaboration with Hampton University, Virginia, materials developed in this project will be assessed for mid- and near-IR emission. Undergraduates at Hampton University and Stanford University will study how to develop lanthanide-containing metal-halides for applications in photonics.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.