In this combined X-ray diffraction and photoluminescence study, the coordination environment of Mn(2+) and the photoluminescence of single Mn(2+) doped KMgBO3 phosphors were studied. Mn(2+) occupies Mg(2+) sites, which were coordinated by six O(2-). The strong absorption of KMgBO3:Mn(2+) was ascribed to the strong relaxation of spin and parity forbidden d-d transitions of Mn(2+). The emission bands were centered at 636 nm, regardless of the excitation wavelength and Mn(2+) doping concentration. Mn(2+) activated KMgBO3 could be efficiently excited with the excitation of Mn(2+) d-d transitions in the wavelength range of 300-475 nm. The red-shift of Mn(2+) emission was because of the strong crystal field environment of Mn(2+) afforded by KMgBO3. The potential applications of the phosphors have been pointed out based on their absorption spectra, excitation and emission spectra, thermal quenching properties, and decay properties.
Zn x ͑ZnO͒ 1−x granular films with nominal atomic concentration of x =0ϳ 1 were prepared by magnetron cosputtering method. Ferromagnetism is observed in films with 0.04Յ x Ͻ 0.60. The room-temperature saturated magnetization increases with increasing x and reaches its maximum value of about 3.34 emu/cc at x = 0.31. The temperature-dependent magnetization curve could be fitted within the framework of Stoner model in a large temperature range from 50 to 800 K. The obtained Curie temperature is higher than 500°C. It is found that the main point defects in ZnO are Zn interstatial and oxygen vacancy. Room-temperature photoluminescence analysis and high-temperature x-ray diffraction measurement show conclusive evidence that the native point defect of Zn interstitial plays a crucial role in the observed magnetic behaviors. By implicating the shallow donor related carriers and/or extending the charge-transfer mechanism to metal/semiconductor heterostructure, the result could be qualitatively explained based on the Stoner theory of band magnetism. These findings may help to get further insight into the ferromagnetic origin in nonmagnetic ion doped ZnO systems.
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