期刊
PHYSICAL REVIEW B
卷 80, 期 23, 页码 -出版社
AMER PHYSICAL SOC
DOI: 10.1103/PhysRevB.80.235421
关键词
cadmium compounds; chemical exchanges; excited states; ferromagnetic materials; ground states; II-VI semiconductors; iron; magnetic polarons; magnetic semiconductors; magnetisation; Mossbauer effect; nanoparticles; paramagnetic resonance; photoluminescence; semiconductor doping; wide band gap semiconductors
资金
- BRNS
- DST India
- UGC India
- CSIR India
- BRNS, India
Chemically synthesized, thiol capped undoped, and Fe doped CdSe nanoparticles (NPs) have been investigated using a variety of physicochemical techniques. The electron spin resonance spectra exhibit two distinct signals at g similar to 4 and g similar to 2 characteristic of Fe(3+) ions occupying highly asymmetric and nearly symmetric lattice sites, respectively. The room temperature Moumlssbauer studies show a broad asymmetric doublet with isomer shift similar to 0.35 mm/sec, quadrupole splitting similar to 0.76 mm/sec characteristic of high spin ferric ions occupying the Cd(2+) sites with associated changes in local lattice environment. The room temperature photoluminescence spectra show transition from excited state Fe(3+) ((4)T(1), (4)T(2), and (4)E) to the ground-state Fe(3+) ((6)A(1)) and also suggest that photoexcited electrons are preferentially transferred to iron ion induced trapping centers in CdSe nanoparticles. Room-temperature ferromagnetism is also observed in thiol capped Fe doped CdSe nanoparticles. Significant changes in saturation magnetization value with increasing iron concentration have been observed. The origin of room temperature ferromagnetism and significant change in M(s) value are discussed in terms of F-center exchange mechanism (bound magnetic polarons).
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