Abstract Mesoporous nanocrystal BaF2 nanopowders (NPs) have been obtained with the pulsed electron beam evaporation (PEBE) technique. The transformation of the structure and morphology of BaF2 nanoparticles (NPles) induced by thermal annealing in air at temperatures of 200, 400, and 900 °C has been monitored with the XRD, SEM, and HRTEM methods. The HRTEM analysis has shown the presence of three polymorph phases (cubic, octahedral, and hexagonal) in the unannealed NP. Upon the transition into the nanoscale, diamagnetic (DM) BaF2 (in the volume state) has demonstrated both paramagnetic (PM) and ferromagnetic (FM) responses at room temperature. The thermal analysis (TA) has confirmed the strong adsorption of CO2 while synthesizingthe BaF2 NP via PEBE method and adsorption of different NOx oxides following irradiation of the BaF2 NP (in air by 700 keV electrons) The appearance of the FM contribution in the diamagnetic BaF2 NP after annealing at a temperature of 600–900 °C is likely associated with the achievement of the percolation threshold with an increase of the BaO oxide concentration. This is in agreement with the well-known theoretical predictions of d0 magnetism in N-doped (C-doped) BaO. The appearance and variations of the FM contribution to the BaF2 NP irradiated by 700 keV electrons are likely connected with an increase of the NOx oxide concentration (due to an increase of the time of electron irradiation), which confirms the hypothesis on the appearance of the FM response in solid-state N (C)-BaO solutions. The FM decrease with time is indicative of the surface character of d0 magnetism in the barium fluoride under study.

中文翻译：

---

BaF2 纳米粉体在热和辐射暴露后的 d0 磁性研究

摘要 利用脉冲电子束蒸发 (PEBE) 技术获得了介孔纳米晶 BaF2 纳米粉体 (NPs)。已使用 XRD、SEM 和 HRTEM 方法监测了通过在空气中在 200、400 和 900 °C 的温度下热退火引起的 BaF2 纳米粒子（NPles）的结构和形态转变。HRTEM 分析表明，在未退火的 NP 中存在三种多晶相（立方、八面体和六边形）。在过渡到纳米尺度后，抗磁性 (DM) BaF2（体积状态）在室温下表现出顺磁性 (PM) 和铁磁性 (FM) 响应。热分析 (TA) 证实了通过 PEBE 方法合成 BaF2 NP 时 CO2 的强吸附和 BaF2 NP 辐照后不同 NOx 氧化物的吸附（在空气中由 700 keV 电子） FM 贡献在抗磁性 BaF2 中的出现在 600-900°C 的温度下退火后的 NP 可能与随着 BaO 氧化物浓度的增加达到渗透阈值有关。这与众所周知的 N 掺杂（C 掺杂）BaO 中 d0 磁性的理论预测一致。FM 对 700 keV 电子辐照 BaF2 NP 贡献的出现和变化可能与 NOx 氧化物浓度的增加有关（由于电子辐照时间的增加），这证实了关于在固态 N (C)-BaO 溶液中出现 FM 响应的假设。FM 随时间降低表明所研究的氟化钡中 d0 磁性的表面特征。