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Controlling material properties at the nanoscale is a critical enabler of high performance electronic and photonic devices. A prototypical material example is VO 2 , where a structural phase transition in correlation with dramatic changes in resistivity, optical response, and thermal properties demonstrates particular technological importance. While the phase transition in VO 2 can be controlled at macroscopic scales, reliable and reversible nanoscale control of the material phases has remained elusive. Here, reconfigurable nanoscale manipulations of VO 2 from the pristine monoclinic semiconducting phase to either a stable monoclinic metallic phase, a metastable rutile metallic phase, or a layered insulating phase using an atomic force microscope is demonstrated at room temperature. The capability to directly write and erase arbitrary 2D patterns of different material phases with distinct optical and electrical properties builds a solid foundation for future reprogrammable multifunctional device engineering.

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The observation of inverted magnetic hysteresis loops and negative magnetic remanence (NRM) in a 7.6 nm thin film of LaSrMnO grown on SrTiO substrates is reported. The film was grown employing pulsed laser deposition and characterized by reflection high-energy electron diffraction during growth and using x-ray reflectivity measurements post-growth. Magnetic properties of the film were measured from 5 K to 400 K under both the field-cooled (FC) and zero-field-cooled (ZFC) conditions. The observed results of inverted magnetic hysteresis loops and NRM are interpreted in terms of the co-existence of a magnetically inhomogeneous region consisting of superparamagnetic spin clusters with a blocking temperature T =  240 K and the ferromagnetic state with an ordering temperature T =  290 K. Hysteresis loop inversion is observed in the temperature region of T < T < T whereas NRM appears in the mixed superparamagnetic and ferromagnetic states for T< T down to 5 K. These observations of hysteresis loop inversion and NRM are related to the magneto-static interaction between the superparamagnetic and ferromagnetic phases leading to anti-alignment of spin of both magnetic phases with respect to each other.

The delafossite CuAlO2 is a rare p-type semiconductor with potential applications as a thermoelectric and as a dilute magnetic semiconductor when doped with transition metal ions. Reported here are results from our investigations of CuAl1-xFexO2 (x = 0, 0.01, 0.05, and 0.1) with a focus on the x-dependence of structural and magnetic properties, and role of impurities. The samples prepared by the solid-state reaction at 1,100°C were characterized by X-ray diffraction (XRD), energy dispersive (X-ray) spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The magnetic results show that the Curie constant (C), low temperature magnetization (M) and the lattice constants scale with x. High resolution M-H loop measurements at 300 K and 10 K show negligible coercivity HC at 10 K but HC ∼ 100 Oe at 300K. These results suggest the presence of minute quantities of hematite (α-Fe2O3) that are not detected in our XRD and XPS. The role of impurities on the published results in this system is discussed.

A series of alkali metal rare-earth borates were prepared via hightemperature flux crystal growth, and their structures were characterized by single crystal X-ray diffraction (SXRD). Na 3 Ln(BO 3 ) 2 (Ln = La-Lu) crystallize in the monoclinic space group P2 1 /n, the potassium series K 3 Ln(BO 3 ) 2 (Ln = La-Tb) crystallize in the orthorhombic space group Pnma, while the Ln = Dy, Ho, Tm, Yb analogues crystallize in the orthorhombic space group Pnnm. To demonstrate the generality of this synthetic technique, high-entropy oxide (HEO) compositions K 3 N d 0 . 1 5 ( 1 ) E u 0 . 2 0 ( 1 ) G d 0 . 2 0 ( 1 ) D y 0 . 2 2 ( 1 ) H o 0 . 2 3 ( 1 ) ( B O 3 ) 2 a n d K 3 Nd 0.26(1) Eu 0.29(1) Ho 0.22(1) Tm 0.14(1) Yb 0.10(1) (BO 3 ) 2 were obtained in single crystal form. Radiation damage investigations determined that these borates have a high radiation damage tolerance. To assess whether trivalent actinide analogues of Na 3 Ln(BO 3 ) 2 and K 3 Ln(BO 3 ) 2 would be stable, density functional theory was used to calculate their enthalpies of formation, which are favorable.

Fast and effective uranyl sequestration is of interest to the nuclear industry. Recently, layered chalcogenide materials have demonstrated fast, selective, and efficient sorption properties toward uranyl cations, and the development and investigation of new types of chalcogenide materials continues to be of interest and represents an intriguing option for uranyl remediation. Three new all-inorganic A 3 Ga 5 S 9 •xH 2 O (A = Rb, Rb/Cs, and Cs) open-framework chalcogenides were obtained via an in situ alkali carbonate to alkali sulfide conversion process achieved under mild hydrothermal conditions. The structures of the all-inorganic openframework chalcogenides consist of a twofold interpenetrated diamond-like 3D framework containing pseudo-T 3 [Ga 10 S 20 ] 10− supertetrahedra. Forty-eight percent of the structural volume is occupied by A + cations and water species, as established by single-crystal X-ray diffraction (SCXRD), infrared (IR) spectroscopy, and energy-dispersive spectroscopy (EDS). The dynamic nature of the A + cations and water molecules within the pores was investigated via SCXRD as well as by IR spectroscopy-monitored H 2 O-to-D 2 O exchange experiments. Framework stability was probed with post-synthetic treatment of A 3 Ga 5 S 9 •xH 2 O (A = Rb and Cs) samples in acidic solutions that resulted in the formation of the oxysulfide (A/H) 3 Ga 5 S 9−y O y •xH 2 O (A = Rb and Cs; y = 0−1), as shown by SCXRD and IR. Ion-exchange studies on A 3 Ga 5 S 9 •xH 2 O (A = Rb and Cs) samples were carried out utilizing a uranyl acetate solution. The presence of the UO 2 2+ species in the ion-exchange product was supported by IR spectroscopy and EDS. Batch method ion-exchange experiments on Cs 3 Ga 5 S 9 •xH 2 O powder demonstrated fast kinetics with 95% uranyl removal from the uranyl acetate solution during the first minute, a maximum uranyl uptake capacity of 15 mg/g, and the subsequent elution of uranyl species with KCl solution. The porous and dynamic nature of the A 3 Ga 5 S 9 •xH 2 O framework coupled with effective UO 2 2+ •••S 2− bonding interactions makes it a good potential sorbent for uranyl remediation from aqueous media.