Laser‐induced phonon and magnon properties of NiO nanoparticles: A Raman study

Abstract

In the present study, the influence of laser intensity on phonon and magnon properties of nickel oxide (NiO) nanoparticles were extensively studied using room temperature Raman spectroscopy. The required NiO nanoparticles were synthesized using a simple sol–gel method. The structural and morphological properties were characterized using powder X‐ray diffraction (XRD), field emission scanning electron microscopy (FE‐SEM), and transmission electron microscopy (TEM) techniques. The rarely reported surface optical (SO) phonon modes of NiO nanoparticles were observed and well‐studied using the dielectric continuum (DC) model. A mismatch between the experimental and DC model SO phonon wavenumbers were observed and is attributed to one magnon‐induced first order phonon shift. The difference between the experimental and DC model SO phonon wavenumbers were reduced with increase in laser power, which indicates the diminishing behavior of magnon excitations. The laser power dependency of highly distinguishable two magnon (2 M) excitation of NiO nanoparticles were well studied. The 2 M modes were experienced a red shift and decrease in intensity with increase in laser power.

Embedding Metal–Organic Frameworks for the Design of Flexible Hybrid Supercapacitors by Electrospinning: Synthesis of Highly Graphitized Carbon Nanofibers Containing Metal Oxide Nanoparticles

“…The Raman peaks at 355 and 515 cm À1 can be ascribed to the NiO vibrational first-order phonon (1 P) modes including transverse optical (TO) and longitudinal optical (LO) modes, while the peaks at 673, 837, and 1063 cm À1 correspond to the secondorder phonon (2 P) modes 2P TO , 2P TOþLO , and 2P LO . [38,39] XPS analyses were also performed to acquire the elemental valence and chemical composition at the surfaces of the samples. Figure 6a shows the XPS full-survey spectra of PANC, FOCNF, and NOCNF.…”

“…The Raman peaks at 355 and 515 cm −1 can be ascribed to the NiO vibrational first‐order phonon (1 P) modes including transverse optical (TO) and longitudinal optical (LO) modes, while the peaks at 673, 837, and 1063 cm −1 correspond to the second‐order phonon (2 P) modes 2P TO , 2P TO+LO , and 2P LO . [ 38,39 ]…”

“…There are also two characteristic peaks at 855.5 eV and 872.5 eV with two satellite peaks at 860.9 and 879.4 eV, corresponding to Ni 2 p 3/2 and Ni 2 p 1/2, respectively, indicating the presence of Ni 2+ in the samples. [ 39 ] The elemental compositions of PANC, FOCNF, and NOCNF are listed in Table 2 . With the increase in MOF amount in the precursors, both Fe and Ni contents increase.…”

On the properties of NiO powders obtained by different wet chemical methods and calcination

“…44,45 Although the 2 M interaction is difficult to be observed in an antiferromagnetic material, 45 the 2 M band in NiO has been widely studied and its dependences with size, temperature, and defect structure, among other parameters, have been well established. [46][47][48] This band, which indicates the existence of an antiferromagnetic order in NiO, 48 arises from superexchange interactions between the next-nearest-neighboring Ni 2+ ions (NNN) in the Ni 2+ − O 2− −Ni 2+ linear atomic chain, 48,49 and in nanostructures, its existence is very sensitive to the presence of point defects. 49 For example, it has been recently reported that Cu 2+ inclusion in NiO nanoparticles results in a decrease in the intensity of the 2 M band, 50 and for bulk NiO film, it has been reported that the absence of the 2 M band responds to phenomena related to a high density of point defects that interfere with the NNN superexchange interaction.…”

“…Although the 2 M interaction is difficult to be observed in an antiferromagnetic material, 45 the 2 M band in NiO has been widely studied and its dependences with size, temperature, and defect structure, among other parameters, have been well established 46–48 . This band, which indicates the existence of an antiferromagnetic order in NiO, 48 arises from superexchange interactions between the next‐nearest‐neighboring Ni 2+ ions (NNN) in the Ni 2+ − O 2− −Ni 2+ linear atomic chain, 48,49 and in nanostructures, its existence is very sensitive to the presence of point defects 49 .…”