Deep in their beautiful lattices, crystals hold secrets about the future of technology and science. Ryan Baumbach aims to find them.
This week at the lab, scientists are using a brand new tool to tweak the crystal structure of materials in the hopes of imbuing them with potentially useful properties.
Using a technique called pulsed laser deposition, physicist Christianne Beekman is creating thin films of materials less than 100 nanometers thick — one one-thousandth the thickness of a sheet of paper. The process involves vaporizing a target material with a class 4 laser, generating a colorful plume of plasma. When that plasma settles on a waiting piece of substrate, the result is a thin film that alters the original structure of the material in a way that can induce new magnetic or electrical properties.
“Sometimes in these complex materials a slight change in the interatomic distance could tip it over to an entirely different phase,” said Beekman. The original “bulk” material might, for example, change from a metal to an insulator in its thin film form (or vice versa) – a nifty trick with potentially powerful applications in electronics and computers. Beekman is also looking at materials that might make excellent solar cells, if photons hitting thin-film versions of them turn out to generate more than one electron per photon.
After creating thin films in this new instrument, Beekman and her team will use MagLab magnets and other facilities to investigate their properties.
“The ability to grow high-quality complex oxide thin films allows us to accelerate materials discovery,” said Beekman, “which will lead to the technologies of tomorrow.”
Video by Stephen Bilenky / Text by Kristen Coyne
Ni3TeO6 provides a new approach to coupling magnetism to ferroelectricity with a record large response. We measured this material's magnetic and electric properties across an extended range of temperature and magnetic field and compared with theoretical calculations to extract a model that describes the underlying reason for a large magnetoelectric coupling. High magnetic fields were key to establishing the magnetic Hamiltonian. This work is motivating the discovery of further 3d-4d oxide materials with large magnetoelectric couplings.
Two researchers play with nanostructures in a fun, fertile physics playground: the space between two things.
The work by Dagan et. al. explores the emergence and coexistence of superconductivity and magnetism at the interface between insulating, non-magnetic LaAlO3 and SrTiO3 nanowires at low temperatures. The effect of the antiparallel magnetic order on the resistance of the 50 nm wide patterned wires follows the form of giant magnetoresistance (GMR) at low applied magnetic fields.
MagLab users have employed a combination of ab-initio theory and a newly developed high-pressure, high-field ferromagnetic resonance technique, which is uniquely sensitive to anisotropic magnetic interactions, to gain insights into the importance of spin-orbit coupling effects in a range of organic materials where this effect is usually considered to be small. The findings may be applicable to topics as diverse as spintronics and topological spin phases.
A novel approach combining pulsed field optical FBG strain measurements in world-class magnets, with Density Functional based calculations to pinpoint the peculiar nanopantograph mechanism behind the magnetoelastic coupling, allows researchers to conclude that magnetic field and pressure are alternative ways to tune the quantum properties of the Shastry-Sutherland compound SrCu2(BO3)2
High magnetic fields have been shown to induce strong electric polarizations in the doped organic quantum magnet, dichloro-tetrakis-thiourea, or DTN. The introduction of disorder in DTN leads to the formation of Bose glass states and the electric polarization is particularly enhanced at the transitions to the glass state.
Grain boundaries in BaFe2As2 (122), which is an iron-based superconductor, block current flow. This study, which was a collaboration with a group at Northwestern University, used a Local Electrode Atom Probe (LEAP), which is a relatively new experimental tool, to make a 3-D atom-by-atom reconstruction of a region of a 122 sample that included a grain boundary. The data showed that the chemical composition varied across the grain boundary and in that oxygen was present at the grain boundaries. These variations in composition may contribute to grain boundary's reduced current carrying capacity.
Square-planar high-spin Fe(II) molecular compounds are rare. Using an easily modifiable pincer-type ligand, the successful synthesis of the first compound of this type that breaks the FeO4 motif was achieved, and the first spectroscopic evidence that the geometry and spin state persist in solution was obtained.