Advances in high-pressure laser floating zone growth: The Laser Optical Kristallmacher II (LOKII).

The optical floating zone crystal growth technique is a well-established method for obtaining large, high-purity single crystals. While the floating zone method has been constantly evolving for over six decades, the development of high-pressure (up to 1000 bar) growth systems has only recently been realized via the combination of laser-based heating sources with an all-metal chamber. While our inaugural high-pressure laser floating zone furnace design demonstrated the successful growth of new volatile and metastable phases, the furnace design faces several limitations with imaging quality, heating profile control, and chamber cooling power.

Ultrafast Enhancement of Ferromagnetic Spin Exchange Induced by Ligand-to-Metal Charge Transfer.

We theoretically predict and experimentally demonstrate a nonthermal pathway to optically enhance superexchange interaction energies in a material based on exciting ligand-to-metal charge-transfer transitions, which introduces lower-order virtual hopping contributions that are absent in the ground state. We demonstrate this effect in the layered ferromagnetic insulator CrSiTe_{3} by exciting Te-to-Cr charge-transfer transitions using ultrashort laser pulses and detecting coherent phonon oscillations that are impulsively generated by superexchange enhancement via magneto-elastic coupling. This mechanism kicks in below the temperature scale where short-range in-plane spin correlations begin to develop and disappears when the excitation energy is tuned away from the charge-transfer resonance, consistent with our predictions.

Mapping the structural, magnetic and electronic behavior of (Eu Ca )IrO across a metal-insulator transition.

In this study, we employ bulk electronic properties characterization and x-ray scattering/spectroscopy techniques to map the structural, magnetic and electronic properties of (Eu Ca )IrO as a function of Ca-doping. As expected, the metal-insulator transition temperature, T , decreases with Ca-doping until a metallic state is realized down to 2 K. In contrast, T becomes decoupled from the MIT and (likely short-range) AFM order persists into the metallic regime.

Mapping the structural, magnetic and electronic behaviour of (EuCa)IrOacross a metal-insulator transition.

In this study, we employ bulk electronic properties characterization and x-ray scattering/spectroscopy techniques to map the structural, magnetic and electronic properties of (EuCa)IrOas a function of Ca-doping. As expected, the metal-insulator transition temperature, T, decreases with Ca-doping until a metallic state is realized down to 2 K. In contrast, the onset of magnetic order at Tbecomes decoupled from Tand (likely short-range) antiferromagnetism persists into the metallic regime.

High-pressure laser floating zone furnace.

The floating zone technique is a well-established single crystal growth method in materials research, which is able to produce volumetrically large specimens with extremely high purities. However, traditional furnace designs have relied on heating from high-powered bulb sources in combination with parabolic mirrors and hence are constrained to transparent growth chambers with large solid angles of optical access. This results in a stark limitation on achievable processing gas pressures and in turn renders a range of compounds unsuitable for crystal growth by the floating zone technique, either due to excessive volatility or due to metastability.