Magnetic characteristics of epitaxial NiO films studied by Raman spectroscopy

Feldl, Johannes; Budde, Melanie; Tschammer, Carsten; Bierwagen, Oliver; Ramsteiner, M.

doi:10.1063/5.0006085

Cited by 20 publications

(10 citation statements)

References 39 publications

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“…According to the Ising cluster model, the frequency of the 2M mode, which is magnetic in origin, can be expressed as where z = 6 (number of the next nearest neighbor NNN), S = 1 (AF spin), J NNN = 19.01 meV, and δ = (1 – c ) defines the concentration of Ni vacancies, and c is the chemical composition of Ni. , The calculated value of δ increases with Sm content, retaining a maximum value of ∼0.12 for the 1% sample, above which δ drops abruptly, confirming Ni deficiency in the Sm-doped samples (inset of Figure b). Furthermore, Figure c shows a plot of variation in the degree of structural order defined as 1 – Q (where Q is the ratio of the integrated area ( I ) of LO and 2M or LO and 2LO) concerning Sm-doping . Analogous to shift in 2M frequencies, 1 – Q is also characterized by a broad valley retaining a minimum of around 1%.…”

Section: Resultsmentioning

confidence: 90%

Sm-Doped NiO Nanoparticles for Magnetic Memory at Room Temperature

Gandhi

Tummala

Chiu

et al. 2021

ACS Appl. Nano Mater.

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The search for diluted magnetic semiconductors (DMSs) has gained immense research interest because of the coexistence of the charge and spin degree of freedom in a single substance to realize a particular class of spintronic devices, and a rare earth (RE)-doped transition-metal oxide (TMO) is one of the choices. This study intends to understand the effect of RE Sm 3+ ion substitution in antiferromagnetic (AF) NiO nanoparticles (NPs) using modern cutting-edge techniques (synchrotron powder X-ray diffraction and soft X-ray absorption, Raman scattering, and superconducting quantum interference device magnetometry). A percolation threshold limit of about 1% incorporation of Sm 3+ ions at the Ni 2+ site was evident. An enhanced magnetic moment observed for an intermediate composition has been attributed to the interacting bound magnetic polaron. A core−shell model has been proposed such that the multivalent point defects reside at the surface of NPs, whereas the core of the particles retains AF properties. The exchange coupling mediated by interfacial frozen spins is the leading mechanism behind the magnetic memory effect at room temperature. The outcome of this study is vital for the future development of RE-functionalized TMO DMS spintronic devices and the understanding of their fundamental physics and chemistry.

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Section: Resultsmentioning

confidence: 90%

Sm-Doped NiO Nanoparticles for Magnetic Memory at Room Temperature

Gandhi

Tummala

Chiu

et al. 2021

ACS Appl. Nano Mater.

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“…The LO+TO and the 2LO(2P) overtones are identified, as well as the two-magnon mode (2M). The 2LO (2P) Raman mode at 1120 cm −1 can be attributed to strains in NiO films while the 2M band (2-magnon mode) at about 1500 cm −1 is measurable as a fingerprint of AFM ordering [29][30][31] originated by the interaction between neighboring (111) Ni +2 planes. Comparing the Raman signal for NiO on both substrates (Figure 3b), a different intensity ratio between the 2M band and the 2P band is noted, which is sensitive to the type of NiO domains that appear in the different crystallographic orientations.…”

Section: Resultsmentioning

confidence: 99%

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Lorenzo-Feijoo,

Serrano,

Hernández-Gómez

et al. 2024

Crystals

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Antiferromagnetic/ferromagnetic (AF/F) systems have been extensively investigated due to the importance that interfacial exchange coupling effects have in the development of magnetic storage technologies. Recently, these systems have garnered interest for the potential they have to imprint the magnetic moments of the AF into an F layer, offering the possibility of using it as a read-out mechanism in antiferromagnetic spintronics. In this study, we explored the importance of crystalline orientation and strains induced by the substrate in the exchange coupling properties of NiO/FeCo AF/F bilayers. For that, we have grown NiO/FeCo bilayers on MgO (001) and Al2O3 (0001) substrates varying the FeCo layer thickness. In addition, we have analyzed both deposited samples and those with induced interfacial unidirectional anisotropy. For inducing such interfacial anisotropy, we used a field cooling procedure, heating the bilayers to 650 K and subsequently cooling down to room temperature under the presence of an external magnetic field of 300 mT. We have investigated the effect of the substrate in terms of crystalline orientation and lattice mismatching on the AF/F exchange coupling as well as the dependence of the coercivity and exchange bias on the inverse F layer thickness that is consistent with the interfacial origin of the AF/F exchange coupling. Moreover, the angular dependence of the magnetic properties was explored by using vectorial Kerr magnetometry, confirming the presence of both magnetocrystalline anisotropy, arising from the epitaxial character of the growing process mainly when the bilayer is grown on MgO (001) substrates, and the field cooling (FC)-induced unidirectional anisotropy.

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“…Moreover, the material offers high chemical stability as well as antiferromagnetic properties with Neel temperature as high as 525 K [5]. All these properties have made NiO a potential candidate for various applications, such as hole transport layer in organic solar cells [6,7], transparent hole conducting films [8], field effect transistors [9,10], UV photo detectors [11,12], exchanged biased systems [13], and spintronic devices [14][15][16].…”

Section: Introductionmentioning

confidence: 99%

“…The p-type conduction in the film can be ascribed to the nickel vacancies (V Ni ) [17][18][19][20]. It is noteworthy that NiO epitaxial films with high crystalline quality have been reported by different growth techniques such as pulsed laser deposition [8,21,22], mist chemical vapor deposition [23], RF magnetron sputtering [24] and molecular beam epitaxy [5] on various substrates, such as sapphire, cubic yttria-stabilized zirconia and MgO. In fact, films with improved crystallinity do not show p-type conductivity, rather these are found to be highly resistive.…”

Section: Introductionmentioning

confidence: 99%

Study of lithium incorporation in (111) NiO epitaxial layers grown on c-sapphire substrates using the pulsed laser deposition technique

Sahu

Yadav

Arora

et al. 2023

J. Phys. D: Appl. Phys.

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Incorporation of Lithium in (111)NiO epitaxial layers grown by pulsed layer deposition (PLD) technique on c-sapphire substrates is studied as functions of growth conditions. The effect of Li-inclusion on the structural, morphological, electrical and optical properties of the films have been systematically investigated. It has been found that the concentration of Li in the film is more at lower growth temperatures. However, the crystalline quality deteriorates as the growth temperature is lowered. The investigation suggests that there is a miscibility limit of Li in NiO. Beyond a critical concentration of Lithium, Li-clusters are detected in the films. Further, it has been found that inclusion of Li gives rise to hydrostatic tensile strain in the NiO lattice that results in the reduction of the bandgap. The study also suggests that Li incorporation improves the electrical conductivity of NiO layers. Ni-vacancy defects also play important role in governing the conductivity of these samples.

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Magnetic characteristics of epitaxial NiO films studied by Raman spectroscopy

Cited by 20 publications

References 39 publications

Sm-Doped NiO Nanoparticles for Magnetic Memory at Room Temperature

Sm-Doped NiO Nanoparticles for Magnetic Memory at Room Temperature

Influence of the Substrate on the Exchange Coupling of NiO/FeCo Bilayers

Study of lithium incorporation in (111) NiO epitaxial layers grown on c-sapphire substrates using the pulsed laser deposition technique

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