Low temperature ferromagnetic FeRh with B2-type crystal structure was successfully synthesized by annealing of the excessively irradiated FeRh thin film samples having nonmagnetic A1-type crystal structure. The B2 phase transformed from the A1 phase by this process contained some amount of lattice defects, such as anti-site defects and vacancies, which made the magnetic spins of the sample aligned. These results imply that the combination of the process of the ion-beam irradiation and annealing of the film samples makes the magnetic state systematically controlled.
Oxysulfide glasses were prepared in a wide range of compositions in the system LiBO2‐LiBS2. Temperatures of glass transition (Tg), crystallization (Tc), and liquidus (Tl) were determined; a maximum of Tg was observed near the composition with 20 mol% LiBS2. The electrical conductivity at 500 K ranges from 5×10−4 to 5×10−3 S·cm−1 with the maxima in conductivity observed near the composition 55LiBO2·45LiBS2. This conductivity enhancement with a mixing of two components, which can be called the mixed‐anion effect, is accompanied by a decrease in the degree of undercooling of glass expressed by the ratio (Tl‐Tg)/Tl. The infrared and Raman spectra showed that the structural units with bridging oxygens B‐O‐B and nonbridging sulfurs B‐S− predominated rather than those with nonbridging oxygens B‐O− and bridging sulfurs B‐S‐B in these glasses.
The nature of the tunneling-assisted hopping conduction in neutron-transmutation-doped GaAs has been studied under photoexcitation with a photon energy of 1.32 eV. It is found that the dopants activated by annealing around 400 °C provide the electrons to the defect levels originating the hopping conduction even when under photoexcitation. The hopping conduction under photoexcitation is affected by quenching in photoconductance below 120 K concerned with the main electron trap (EL2) and/or the As antisite defect (AsGa) induced by the neutron irradiation. The photoconductance of the samples with a lower radiation damage, AsGa≤1×1018 cm−3, consists of the coexistence of the hopping and band conductions.
In neutron transmutation doping (NTD) to the undoped semi-insulating GaAs, a new annealing stage related to the tunneling assisted hopping conduction was found around 400 °C for fast neutron fluences of ≥7.0×1017 n/cm2. It is suggested that this stage is based on the enhancement in the hopping conduction by the activated dopant in the NTD process. The stage was not observed for the irradiation with a small amount of fast neutrons. The activation energy for the annihilation of As antisite defects (AsGa) was found to be 0.9 eV. The annealing temperature to achieve the desired carried concentration increased with the fast neutron fluence.
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