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Abstract Magnetic refrigeration around the liquid-helium temperature plays a critical role in many technological sectors. Even if gallium gadolinium garnet (GGG) has been regarded as the benchmark, its application is highly limited by the small magnetic entropy changes, the requirement of superconducting magnets, and the large device sizes. Here, we report that LiREF4 (RE = rare earth) single crystals exhibit significantly superior magnetocaloric performance levels to commercial GGG. Under a small magnetic field of 5 kOe, which can be easily achieved by a permanent magnet, the magnetic entropy change reaches a record-high value of 16.7 J kg−1 K−1 in LiHoF4 in contrast to the value of 1.0 J kg−1 K−1 in GGG. The combination of small driving fields, large entropy changes, and excellent thermal and/or magnetic reversibility enables this series to be employed as the ideal working material for compact magnetic refrigeration around the liquid-helium temperature.

Ce:Li _6 Y(BO _3 ) _3 (LYBO) is a well-known candidate for thermal neutron detection with a very high Li concentration (3.06 × 10 ^22 /cm ^3 ). So far, as-grown crystals exhibit a milky appearance that compromises their performance as scintillators. Current work demonstrates, for the first time, the growth of scattering-free undoped and Ce-doped LYBO by a thermal quenching process. The origin and features of the scattering centers are investigated in detail. Furthermore, the annealing treatment for the scintillation activation is studied, finding that the reduction in oxygen vacancies is mandatory. Under thermal neutron irradiation, the annealed scattering-free Ce:LYBO single crystal achieves a record-high light yield of 6200 ph/n in a single decay with a lifetime as short as 24 ns.

The halide vapor phase epitaxy of α-Ga2O3 is demonstrated for the first time. The films are twin-free and heteroepitaxially grown on sapphire (0001) substrates using gallium chloride and oxygen as precursors. X-ray ω–2θ and pole figure measurements reveal that the film is single-crystalline (0001) α-Ga2O3 with no detectable formation of β-Ga2O3. The optical bandgap is determined to be 5.16 eV based on the transmittance spectrum. The growth rate monotonically increases with the partial pressures of the raw material gases, reaching approximately 150 µm/h, which is over two orders of magnitude larger than those of conventional vapor phase epitaxial growth techniques, such as mist CVD or MBE. [ABSTRACT FROM AUTHOR]