Polarized Raman scattering in helimagnetic β‐MnO₂

Abstract

A rutile b-MnO 2 film was grown on MgO substrate using plasma-assisted molecular beam epitaxy (PAMBE) monitored by reflection high-energy electron diffraction (RHEED). Polarized Raman spectra at various temperatures were obtained to investigate the influence of the helimagnetic structure on the vibrational modes of b-MnO 2 . A red shift of E g modes indicates a gradual formation of spin angles between neighboring Mn 4+ ions. The intensities of the E g and A 1g modes with y-polarized incidence increase remarkably below the Néel temperature. A new view as vibrational mode projection (VMP) indicates the interactions between the magnetic component of incident light and the helimagnetic structure.

Influence of Stress and Defect on Magnetic Properties of Mn3O4 Films Grown on MgAl2O4 (001) by Molecular Beam Epitaxy

“…Many manganese oxide films have been grown on MgO (001), LaAlO 3 (001), and other substrates by using plasma-assisted molecular beam epitaxy (customized system, Omicron) in our previous works. , The MgAl 2 O 4 substrates were degreased by successive supersonic cleaning in acetone, ethanol, and deionized water, then annealed at 770 K for 30 min in O 2 atmosphere as usual . Because the growth rate plays an important role in determining the structural phase in order to enhance the growth rate, the temperature of the Mn effusion cell was set at 1180 K (with a growth rate about 7 Å/min).…”

Recent advances in linear and non‐linear Raman spectroscopy. Part III

“…[162] The polarised Raman scattering from films of helimagnetic β-MnO 2 on MgO substrates were obtained at various temperatures in order to investigate the influence of the helimagnetic structure on the vibrational modes of β-MnO 2 . [163] Baratta et al [164] studied the Raman scattering from ion-radiated astrophysically relevant solid materials. An in situ Raman study of mineral phases formed as by-products in a rotary kiln for clinker production was published by Gastaldi et al [165] MicroRaman spectroscopy was used for the study of solid and liquid inclusions within natural samples of corrundum (Al 2 O 3 ) from various continents.…”

Plasma-Assisted Chemical Vapor Deposition of F-Doped MnO2 Nanostructures on Single Crystal Substrates

“…MnO 2 exhibits at least six different structurally related crystalline modifications (α, β, γ, δ, ε, and λ) [1, 2,4,7,10,[16][17][18][19]. All these polymorphs are semiconductors with low resistivity [2,20,21], and have emerged as attractive candidates for several end-uses, including electrodes in Li-and Na-ion batteries and supercapacitors, thermoelectric materials, chemical sensors, photo-and electrocatalysts for pollutant degradation and hydrogen production, and magnetic devices useful for information storage [5,8,[11][12][13][14][15]18,[21][22][23][24][25][26][27][28][29][30][31][32][33]. Among MnO 2 polymorphs, the most stable and abundant, i.e., rutile-type β-MnO 2 (pyrolusite) [16,34,35], is composed of MnO 6 octahedra linked by corner-shared oxygens into tunnel-containing frameworks [4,9,23,36].…”

“…Amid the various applications, the interest in β-MnO 2 has been promoted by its screw-type magnetic structure with an important spin-lattice coupling, as well as by the large room temperature magnetoresistance and ferromagnetism. Altogether, these features are of considerable importance from both a fundamental and a technological point of view, since they can give rise to applications in recording devices and contribute to new studies on electronic-magnetic interactions in the target systems [16,24,25,35,37].…”

“…Films of the most stable β-MnO 2 polymorph have been obtained by ALD on Al 2 O 3 (012), SiO 2 (001), and MgO(100) [1, 2,21] by PA-MBE on Si(100), MgO(001), TiO 2 (110), and LaAlO 3 (001) [4,20,24,25,28], and by pulsed laser deposition (PLD) on Si(100) [5]. Nevertheless, various of these processes involved relatively harsh conditions either in terms of reaction atmosphere (e.g., use of ozone [1,2,6,21,31,32]) or of the used power/temperature [4,5,24,25,27,28,30]. In view of possible practical applications, the availability and implementation of milder and flexible preparative procedures enabling a good control over material structure, morphology, and functional properties represent an important requirement [45].…”