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Diverse Spectroscopic Studies and First-Principles Investigations of the Zinc Vacancy Mediated Ferromagnetism in Mn-Doped ZnO Nanoparticles

机译:Mn掺杂的ZnO纳米颗粒中锌空位介导的铁磁性的多种光谱研究和第一性原理研究

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A systematic study on the room temperature ferromagnetism (RTFM) in undoped and Mn-doped ZnO nanoparticles (NPs) prepared by the coprecipitation method has been reported. The neutral and singly ionized zinc vacancy defects exhibited in the results of photoluminescence (PL), micro-Raman spectroscopy, and electron paramagnetic resonance (EPR) studies are found to be of ferromagnetic origin in bare ZnO, and it has been confirmed that Mn2+ ions substitutionally enter at Zn2+ sites in wurtzite ZnO. The results of positron annihilation and coincidence Doppler broadening measurements corroborate the Zn vacancies and their clusters. It is observed that in Mn:ZnO, the magnetic ordering is changed from ferro-to paramagnetic because of interacting adjacent Mn-Mn ions. The higher saturation magnetization of 565 x 10(-3) emu/g is explained by a quasi indirect exchange mechanism based on the interaction of bound magnetic polarons formed by the Zn vacancies (V-zn) and nearby Mn ions. Further, first principle calculations reveal the magnetic centers in nonmagnetic ZnO with V-zn and the stable ferromagnetic ordering in Mn:ZnO at the optimum distance of Mn-Mn approximate to 3.26 angstrom.
机译:对通过共沉淀法制备的未掺杂和锰掺杂的ZnO纳米颗粒(NPs)中的室温铁磁性(RTFM)进行了系统研究。在光致发光(PL),显微拉曼光谱和电子顺磁共振(EPR)研究的结果中显示出中性和单个离子化的锌空位缺陷,它们是由裸露的ZnO产生的铁磁性,并且已证实Mn2 +离子替代地进入纤锌矿型ZnO中的Zn2 +位点。正电子an没和巧合多普勒展宽测量的结果证实了锌空位及其簇。可以看出,在Mn:ZnO中,由于相邻的Mn-Mn离子相互作用,其磁序从铁磁变为顺磁。 565 x 10(-3)emu / g的更高饱和磁化强度是由基于锌空位(V-zn)和附近的Mn离子形成的结合磁极化子相互作用的准间接交换机制解释的。此外,第一原理计算揭示了具有V-zn的非磁性ZnO中的磁心,以及在Mn-Mn的最佳距离约为3.26埃时Mn:ZnO中的稳定铁磁有序。

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