Spectra Of Crystals Research Articles

Electronic and optical properties of computationally predicted Na-K-Sb crystals

Abstract Thanks to their favorable electronic and optical properties, sodium-potassium-antimonides are an emerging class of crystals used as photocathodes in particle accelerators. The persisting challenges related to the synthesis and characterization of these materials demand support from theory and make the study of computationally predicted polymorphs particularly relevant to identifying the structure, composition, and properties of the samples. Using first-principles methods based on density functional theory and many-body perturbation theory, the electronic and optical properties of cubic NaK2Sb and hexagonal Na2KSb are studied. Both systems, experimentally reported in the hexagonal and cubic phase, respectively, exhibit an indirect fundamental gap that is energetically very close to the direct band gap at Γ of magnitude 0.81 eV for NaK2Sb and 0.70 eV for Na2KSb. In the band structure of both materials, Sb p-states dominate the valence region with minor contributions from the alkali p-states, while the alkali s-states mainly contribute at lower energies. The optical spectra of both crystals are not subject to sizeable excitonic effects, except for a redshift of the excitation energies of 50-100 meV and some redistribution of the oscillator strength beyond the lowest-energy peak in the near-infrared region. Our results indicate that computationally predicted cubic NaK2Sb and hexagonal Na2KSb have favorable characteristics as photocathodes and, as such, their presence in polycrystalline samples is not detrimental for this application.

Symmetry analysis of Raman spectra of crystals based on angular dependencies

Suggested a method to reconstruct the Raman scattering tensor by studying the angular dependences of Raman line intensities in tiny unoriented microcrystals. The method was verified on well-known calomel Hg2Cl2 model crystals. The spectral line phase-indicators in the Raman spectra reveal different symmetry types of DUT-8 (Ni) metal-organic framework crystals in the open pores and closed pores phases. A technique can be used to reconstruct the Raman scattering tensor of any unoriented crystalline samples.

Excitations in layered materials from a non-empirical Wannier-localized optimally-tuned screened range-separated hybrid functional

Accurate prediction of electronic and optical excitations in van der Waals (vdW) materials is a long-standing challenge for density functional theory. The recent Wannier-localized optimally-tuned screened range-separated hybrid (WOT-SRSH) functional has proven successful in non-empirical determination of electronic band gaps and optical absorption spectra for covalent and ionic crystals. However, for vdW materials the tuning of the material- and structure-dependent functional parameters has only been attained semi-empirically. Here, we present a non-empirical WOT-SRSH approach applicable to vdW materials, with the optimal functional parameters transferable between monolayer and bulk. We apply this methodology to prototypical vdW materials: black phosphorus, molybdenum disulfide, and hexagonal boron nitride (in the latter case including zero-point renormalization). We show that the WOT-SRSH approach consistently achieves accuracy levels comparable to experiments and many-body perturbation theory (MBPT) calculations for band structures and optical absorption spectra, both on its own and as an optimal starting point for MBPT calculations.

Role of BPO4 flux in BaBPO5 crystal growth characterized through high-temperature Raman spectroscopy

In this study, we explored the growth of incongruently melting crystals in a starting solution with flux to better understand the role of flux in crystal growth mechanisms. We recorded the spectrum of BaBPO5 crystals across a 200-1400 cm−1 range for detailed Raman spectroscopic analysis. The observed Raman bands corresponded to the vibrations of PO4 and BO4 units. These units link with B-O-P bonds via common corners to form PBO7 groups that serve as basic structural units of the crystal. Notably, these PBO7 structures remain stable at high temperatures up to the crystal melting point, at which the isolated PO4 groups predominantly exist in the melt, as revealed by high-temperature Raman spectroscopy. Further investigations into the Raman spectra of the starting solution enriched with BPO4 self-flux indicate that PBO7 groups are crucial for crystal growth. The addition of PBO4 flux aids in the formation of these PBO7 units. This research paves the way for expanding our understanding to other systems, which will help elucidate the mechanisms behind crystal growth.

OPTICAL PROPERTIES OF THE AgBiP2Se6 SINGLE CRYSTAL

The AgBiP2Se6 compound has emerged as one of the most studied hexachalcohypodiphosphates in recent years. This is interest is driven by its distinctive layered structure, which implies the possibility of obtaining monolayers and the observation of various of quantum effects. Most studies to date, however, have focused on first-principles calculations, while experimental investigations have primarily been limited to structural analysis and stoichiometric composition determination. This work partially addresses the gap in research by exploring the optical properties of AgBiP2Se6. Transmission spectra within the optical range of 220-1400 nm, as well as Raman spectra, were obtained from single crystalline AgBiP2Se6 samples. The band gap, determined from the transmission spectra using the graphical Tauc method, was found to be 1.44 eV. This value aligns closely with the DFT band-structure calculations using the Perdue-Burke-Erzenhorf (PBE) model without a Hubbard correction parameter (1.384 eV). The Raman spectrum of the AgBiP2Se6 crystal reveals five distinct peaks at approximately 68, 125, 169, 436, and 462 cm-1. The peak at 68 cm-1 can be attributed to the vibrational mode of the cationic centers; the peaks at 125 and 169 cm-1 can correspond to deformations within the Se-P-P and Se-P-Se bonding systems involving changes in bond angles; and the peaks at 436 and 462 cm-1 reflect bond length changes within the anionic (P2Se6)4-group.

Characterization of the Microstructure of Sr0.75Ba0.25Nb2O6 Thin Films by Brillouin Light Scattering.

Strontium-barium niobate (SrxBa(1-x)Nb2O6) films can be considered as a promising material for microwave applications due to high dielectric nonlinearity and relatively low losses. Since strontium-barium niobate has a disordered structure that determines its unique electrical properties, the identification of structural features of the SrxBa(1-x)Nb2O6 films is the key to their successful use. The SrxBa(1-x)Nb2O6 films were synthesized on a sapphire substrate by magnetron sputtering. The structure of the films was studied by both traditional methods of electron microscopy, X-ray diffraction, and the rarely used for thin films investigation Brillouin light scattering method, which was the focus of our study. We show that Brillouin light scattering is an excellent nondestructive method for studying the structural features of thin ferroelectric strontium-barium niobate films. An analysis of the features of the Brillouin light scattering spectra in thin-film structures and their comparison with the spectra of bulk crystals allowed us to determine with high accuracy the thickness of the films under study and their structural features determined by the resonant scattering of acoustic waves.

Raman scattering of omphacite at high pressure: Toward its possible application to elastic geothermobarometry

Abstract Due to their widespread occurrence in several geological settings, omphacite inclusions could be used for elastic Raman geothermobarometry. However, the Raman scattering of complex silicate minerals entrapped in a host depends on both the chemical composition and elastic strain developed during the metamorphic pathway, which makes the task very challenging. Here, as a very first step to probe the potential of omphacite to be used as a mineral inclusion in elastic geothermobarometry, we report the pressure dependence of the Raman spectra of omphacite crystals with the same composition, approximately Jd43Di57, but having different symmetry because of the existence (P2/n) or absence (C2/c) of chemical order at the six- and eight-coordinated cation sites. The experimental results are complemented by ab initio quantum mechanical simulations on fully ordered omphacite (Jd50Di50). We demonstrate that the position of the well-resolved Raman peak near 688 cm–1, arising from Si-O-Si bond bending, is very sensitive to pressure but independent of the state of chemical order, which makes it promising to be utilized in Raman geobarometry. The width of this peak varies with chemical order but not with pressure and therefore can be used to constrain the temperature of inclusion entrapment, because the chemical order is indicative of the closure temperature of the cation-exchange reaction. However, further detailed analyses on the compositional variation of the Raman spectra of omphacite is required before considering omphacite-in-garnet systems to be suitable for Raman elastic geothermobarometry.

Αlpha-Ray Detection Properties of Spinel Single Crystals

A scintillator is one of the phosphors for radiation detection. Typical application fields of scintillators are medical, security, and environmental dosimetry. In nuclear facilities, there are high doses of α-ray, and monitoring of α-ray is necessary. Up to now, Ag-doped ZnS is used for α-ray detection. Although Ag-doped ZnS has high light yield, the detection efficiency is limited because the material form is opaque polycrystal. Therefore, a novel scintillator with high transparency is required for α-ray detection. Spinel materials are one of the candidates for radiation detection because of their high radiation resistant. According to the previous study, scintillation properties of MgGa2O4 and ZnGa2O4 have been studied under γ-ray irradiation. On the other hand, these materials seem to be suitable for α-ray detection rather than γ-ray detection because of the low effective atomic number. In addition, other spinel materials also worth studying. In this study, we synthesized MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals and evaluated the optical and scintillation properties.The starting powders were MgO, ZnO, Al2O3, Ga2O3. The powders were mixed into homogeneously and shaped into cylindrical rods by packing into balloon and applying hydrostatic pressure. Then, the rods were sintered 1400°C for 8 h in air to obtain ceramics precursor. Single crystalline samples were synthesized by the floating zone method using the ceramics precursor. For measurements, the synthesized crystals were processed to approximately 5 mm in diameter and 1 mm in thickness by cut and polishing.The transparent and single-phase of the MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals were successfully obtained by the floating zone method. According to the total transmission spectra, the total transmittances of the crystals were 70−80% in visible region. In the X-ray-induced scintillation spectra, MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals showed a luminescence peak around 380, 400, 300, and 350 nm, respectively. The luminescence origin of each crystal was considered to be due to oxygen vacancies of the host materials. Figure 1 shows the pulse height spectra of the spinel crystals under 241Am α-ray irradiation. The spectra of a commercial Bi4Ge3O12 (BGO, 8000 ph/MeV) single crystal under 137Cs γ-ray irradiation is also shown as a reference. As shown in Figure 1, all the crystals showed a clear full energy peak. From the comparison with the peak position of BGO, the light yields of the MgAl2O4, MgGa2O4, ZnAl2O4, and ZnGa2O4 single crystals were 200, 4300, 700, 5700 ph/5.5MeV-α, respectively. The details will be discussed in the conference. Figure 1

Donepezil hydrochloride fingerprint spectral and formation mechanism analysis.

Donepezil hydrochloride is a widely used medication for treating Alzheimer's disease. This study utilized terahertz time-domain spectroscopy to analyze the fingerprint spectra of donepezil hydrochloride, identifying five characteristic absorption peaks at 1.65, 2.44, 2.56, 3.31, and 3.75THz. The vibrational spectrum of the donepezil hydrochloride crystal was further examined using solid-state density functional theory. Based on simulation calculations, the characteristic peaks were identified and analyzed in detail, focusing on long-range ordering and weak interaction networks. The results demonstrate that terahertz spectroscopy is an effective tool for studying intermolecular interactions in drug crystals.

Solvatochromism, electric dipole moments, optical properties and electronic structure of biphenylcarbonitrile liquid crystals

The UV–Vis. absorbance and fluorescence spectra of 4HC (4′-heptyl-4-biphenyl carbonitrile) and 4OB (4′-Octyl-4-biphenylcarbonitrile) liquid crystals were measured in 23 solvents with different polarities. As dependent on changing of solvents, while the change in absorbance spectrum of liquid crystals have less, change in fluorescence spectrum have more. Molecular interactions were quantitavely investigated by using Linear solvation energy relationships. Optical forbidden energy gap has been determined with using Tauc plot. The refractive index has been calculated with semi-empirical methods. The relationships between refractive index and Eg has been commented in n-hexane, acetic acid, water and 1,4-dioxane. The electric dipole moment has been calculated by using the Bilot-Kawski, Lippert-Mataga, Bakshiev, Kawski-Chamma-Viallet and Reichardt methods. Solvatochromic shifts showed to having large dipole moments of 4OB and 4HC LCs. Their molecular orbital energies, electric dipole moments, MEP, SAS, and reactivity properties of 4HC and 4OB LCs has been found by quantum chemical calculations. It was observed that the dipole moment of 4HC was higher than 4OB.

Enhanced emission and surface modification in ZnO treated with Ar, H, and O plasmas

Plasma treatment is a crucial technique for manipulating the optoelectronic properties of ZnO devices by modifying surface defects. The choice of plasma gas in the treatment process significantly influences these defects, as evidenced by the luminescence characteristics. In this paper, significant differences have been observed in the photoluminescence spectra of ZnO films and single crystals before and after treatment with three kinds of plasma gas. After Ar and H plasma treatment, the UV emission is significantly enhanced up to 1000 times, while the visible emission is suppressed. Conversely, after O plasma treatment, the UV emission remains unchanged, but the deep level emission exhibits a subtle transformation. Since the influence depth of plasma treatment is confined to the surface, all these alterations of typical luminescence are strongly dependent on surface-related defects, thereby challenging the previous interpretation that they originate from bulk defects. The modification effects of various plasmas on surfaces are confirmed from multiple perspectives, and the mechanisms behind the enhancement or suppression of luminescence are systematically analyzed. A comprehensive understanding of plasma treatment, along with precise control of surface defects, is crucial for optimizing the performance of ZnO devices.

One-Dimensional Photonic Crystals Comprising Two Different Types of Metamaterials for the Simple Detection of Fat Concentrations in Milk Samples.

In this study, we demonstrate the reflectance spectrum of one-dimensional photonic crystals comprising two different types of metamaterials. In this regard, the designed structure can act as a simple and efficient detector for fat concentrations in milk samples. Here, the hyperbolic and gyroidal metamaterials represent the two types of metamaterials that are stacked together to construct the candidate structure; meanwhile, the designed 1D PCs can be simply configured as [G(ED)m]S. Here, G refers to the gyroidal metamaterial layers in which Ag is designed in a gyroidal configuration form inside a hosting medium of TiO2. In contrast, (ED) defines a single unit cell of the hyperbolic metamaterials in which two layers of porous SiC (E) and Ag (D) are combined together. It is worth noting that our theoretical and simulation methodology is essentially based on the effective medium theory, characteristic matrix method, Drude model, Bruggeman's approximation, and Sellmeier formula. Accordingly, the numerical findings demonstrate the emergence of three resonant peaks at a specified wavelength between 0.8 μm and 3.5 μm. In this context, the first peak located at 1.025 μm represents the optimal one regarding the detection of fat concentrations in milk samples due to its low reflectivity and narrow full bandwidth. Accordingly, the candidate detector could provide a relatively high sensitivity of 3864 nm/RIU based on the optimal values of the different parameters. Finally, we believe that the proposed sensor may be more efficient compared to other counterparts in monitoring different concentrations of liquid, similar to fats in milk.

Features of the defect structure of a lithium-gradient nonlinear optical single crystal LiNbO3 and their manifestation in the Raman spectra

LiNbO3 crystal with a lithium composition gradient of Li/Nb = 0.8 wt%/cm (Li0.97..1.01Nb1.03..0.99O3) were obtained. A monotonic change in the edge of the UV absorption edge is observed when scanning the surface of the gradient crystal along the growth direction. Raman spectra from different areas of studied crystal were analyzed in a wide frequency range, which includes the region of fundamental vibrations of the crystal lattice (100–900 cm−1) and the region of overtone processes (900–3000 cm−1). A compositionally homogeneous, congruent LiNbO3 crystal was used as a comparison sample. It was found that in the spectra obtained from different parts of the gradient crystal, there is a significant scatter in the frequency values of the lines corresponding to the fundamental vibrations of the crystal lattice, but at the same time, the number of lines corresponding to the fundamental vibrations of the lattice for the gradient and compositionally homogeneous LiNbO3 crystals is the same. Moreover, in the spectrum of a gradient crystal in the region of overtone processes of fundamental vibrations, significantly more lines (35 lines) are observed than in the spectrum of compositionally homogeneous crystals (15 lines). The data obtained show that the state of the defect structure of compositionally homogeneous crystals and gradient LiNbO3 crystal is significantly different. The discovered differences between the defective structure of a gradient crystal and the defective structure of a compositionally homogeneous crystal may be the reason for compensation (damping) of distortions during nonlinear optical conversion of laser radiation by a gradient crystal due to the uneven temperature distribution along the length of the crystal. In compositionally homogeneous crystals, such temperature distortions significantly limit the efficiency of nonlinear optical conversion.

Piezo-optical properties and infrared spectra of Rb2SO4 crystals

The paper deals with the dispersion dependences of birefringence Δni(λ) of the mechanically free and uniaxially clamped Rb2SO4 crystal along different crystal-physical axes at room temperature. It was found that the crystal has an insignificant normal dispersion d(Δnx)/dλ χ ≤ 0, and uniaxial compressions σm do not change the character, but only the slope of the dependences Δni(λ). Uniaxial loads shift the position of the optical isotropic point both in the short-wavelength (σz) and in the long-wavelength part of the spectrum (σy). The spectral dependences of the combined piezo-optical coefficients πkmo(λ) were calculated and it was found that they have an insignificant dispersion dependence, and the absolute values of the piezo-optical coefficients π31o and π21o are equal to each other in the vicinity of the optical isotropic point at the light wavelength λ = 490 nm. The reflection spectra of Rb2SO4 crystals were measured in the infrared range at room temperature using FT-IR spectrometer and synchrotron radiation and the corresponding ab initio calculations of the phonon partial density of states and the dielectric function were performed.

The Crystal Chemistry of Boussingaultite, (NH4)2Mg(SO4)2·6H2O, and Its Derivatives in a Wide Temperature Range

The crystal structure, thermal behavior, and vibrational spectra of the anthropogenic analogue of boussingaultite, (NH4)2Mg(SO4)2·6H2O, and its dehydrated counterpart efremovite, (NH4)2Mg2(SO4)3, were studied in detail. The sample from the Chelyabinsk burning coal dumps has the composition of (NH4)1.92(Mg1.02Mn0.01Fe0.01)∑1.04(SO4)2·6H2O and crystallizes in the space group P21/a, with a = 9.3183(4), b = 12.6070(4), c = 6.2054(3) Å, β = 107.115(5)°, V = 696.70(5) Å3 (at 20 °C), Z = 2. The thermal evolution steps are as follows: boussingaultite (NH4)2Mg(SO4)2·6H2O (25–90 °C) → X-ray amorphous phase (100–150 °C) → efremovite (NH4)2Mg2(SO4)3 (160–340 °C) → MgSO4 Cmcm + Pbnm (340–580 °C) → MgSO4 Pbnm (580–700 °C). Thermal expansion is anisotropic, with the coefficients (×106 °C−1) α11 = 52(2), α22 = 68(2), α33 = –89(3), and αv = 31(3) at T = –123 °C; and α11 = 53(2), α22 = 67(2), α33 = 15(1), and αv = 136(3) at T = 60 °C. The maximal thermal expansion is along the b-axis and is due to straightening of corrugated pseudolayers (within the ab plane) of Mg(H2O)6 octahedra and SO4 tetrahedra with NH4 groups in the interlayer space. Vibrational spectroscopy outlines the general trend of dehydration and deammonization as the difference in the temperature intervals of these transformation steps allows separation of O–H and N–H vibrations in the process of dehydration by infrared and Raman spectroscopy. The intermediate partially dehydrated modification of boussingaultite was detected by in situ Raman spectroscopy at 110 °C that may correspond to ammonium leonite.

The infrared spectrum of the protic ionic liquid 1-methylimidazolium nitrate: An ab initio molecular dynamics simulation study

Complex features observed in the infrared (IR) spectrum of the protic ionic liquid 1-methylimidazolium nitrate, [C1im][NO3], are assigned using ab initio molecular dynamics (AIMD) simulation. AIMD is used at the same level of theory to simulate the known X-ray crystal structure of [C1im][NO3] and a cluster of ionic pairs representing the liquid phase. The calculation of several single particle and collective time correlation functions of velocity forms the basis for the AIMD simulation assignment of the infrared spectra. The AIMD simulation demonstrates that the lift of the degeneracy of the anion asymmetric stretching mode, νas(NO3), due to symmetry breaking and coupling to external modes result in multiple band splitting in the crystal spectrum in the region of the νas(NO3) mode. Owing of the intrinsic anharmonic characteristic of the AIMD simulation, the calculation accounts for the broad band in the high-frequency range of the IR spectrum caused by the cation ν(NH) stretching mode in strong cation–anion hydrogen bond. The AIMD simulation of the liquid captures spectral changes upon melting of [C1im][NO3] due to loosening of the NH···O hydrogen bond and changes in the [NO3]- interaction with other hydrogen atoms of the imidazolium ring. The AIMD simulation assigns the intermolecular stretching mode of the hydrogen bond, ν(NH…O), as the band at 183 cm−1 in the far infrared spectrum of the [C1im][NO3] crystal.

Crystal growth, spectra and laser properties of Tm3+ and Ho3+ co-doped GdScO3 crystal

Tm,Ho:GdScO3 single crystal was grown by the Czochralski method. Its quality and effective segregation coefficient of crystal were characterized, and spectral properties of crystal (100) plane were studied. The absorption cross-section of Tm,Ho:GdScO3 at 793 nm is 1.61 × 10−20 cm2 and emission cross-section at 2020 nm is 1.39 × 10−20 cm2. The laser performance of the crystal by 793 nm LD end-pumped was investigated. The maximum output power of 240 mW was obtained with a slope efficiency of 9.1 % in CW(continuous wave) pump mode. In pulse mode, the maximum average output power of 507 mW was achieved. The maximum slope efficiency of 13.7 % was obtained with 100 Hz and 400 μs. The laser wavelength was 2096 nm. The beam quality factors Mx2/My2 were fitted to be 1.81/1.80. These results indicate that Tm,Ho:GdScO3 crystal is a promising candidate medium for near-infrared laser application.

Microstructural, dielectric, electrical, electromagnetic, and magnetic property enhancements in GdIG /TrIG/ Mn0.2Co0.3Zn0.5Fe2O4 ferrites composites for electronic devices application

Gadolinium garnet ferrite (GdIG) and terbium garnet ferrite (TrIG), known for their favourable magnetic and dielectric characteristics, were combined with doped zinc spinel ferrite (GdIG)x-(TrIG)y/Mn0.2Co0.3Zn0.5Fe2O4(1-x-y) (at x=1 y=0, x=0 y=1, x=y=0.5, x=y=0.25, x=y=0) to achieve improved permittivity, permeability and magnetic properties with reduced magneto-dielectric losses. Our study details the synthesis process and the resulting enhancements in structural, magnetic, and dielectric properties of the prepared samples. Analysis of the X-ray diffraction (XRD) patterns confirmed the presence of a crystalline structure characterized by both cubic spinel and cubic garnet phases in the composites. The microstructures of the composites were analysed with field emission scanning electron microscopy (FESEM), revealing the variation in a grain size from 0.11 μm to 0.96 μm at x =y=0.5. A thorough link between the crystal structure and XRD spectra, transmission electron microscope (TEM), and selected area electron diffraction (SAED) patterns have all been investigated in order to enhance the characterisation of the samples. At 1KHz, the composites exhibit highest electrical resistivity values of 5.9×106 Ωm and 2.6×106 Ωm. With the incorporation of spinel ferrites in garnet ferrite composite (x=y=0.25) the highest value of dielectric constant (885.2) and low value of dielectric loss (0.07) at 100 KHz has been obtained. Permeability values, derived from permittivity data, showed an increase in real permeability values of from 1.4×1012 to 9.2×1017 for x=y=0.5 to x=y=0.25 composite. Vibrating sample magnetometer (VSM) further confirm that the composite x=y=0.25 has highest magnetic saturation (148.8 emu/g), coercivity (502 Oe) and microwave operating frequency (33.6 GHz). The observed high dielectric constant, low loss values, switching field distribution and good magnetic properties suggest the potential suitability of these samples for various electronic devices like: high frequency devices, antennas, switching devices and magnetic recording devices.

Absorption Spectra of AlGaN/GaN Terahertz Plasmonic Crystals-Experimental Validation of Analytical Approach.

Absorption spectra of AlGaN/GaN grating-gate plasmonic crystals with a period from 1 µm to 2.5 µm were studied experimentally at T = 70 K using Fourier-transform infrared spectrometry. The plasmonic crystals exhibit distinct absorption lines of various plasmon harmonics across the 0.5 to 6 THz frequency range, tunable by gate voltage. Cumbersome and time-consuming electromagnetic simulations are usually needed to interpret or predict the grating-gate crystal spectra. In this work, we examine an analytical model and show that it can successfully describe the majority of existing experimental results. In this way, we demonstrate a new analytical platform for designing plasmonic crystals for THz filters, detectors, and amplifiers.

Thin Ga(Sb,P)/GaP quantum wells with indirect band gap: Crystal structure, energy spectrum, exciton recombination and spin dynamics

Heterostructures with thin GaSb layers embedded in a GaP matrix are studied by transmission electron microscopy as well as steady-state and transient photoluminescence. For a single, one monolayer thick deposition with subsequent overgrowth, nonmonotonic Sb segregation results in self-organized Ga(Sb,P) double-quantum well (QW) formation. One QW is positioned deep in GaP at the designated place according to the heterostructure design, and the other QW is in the near surface region after 40 monolayers of GaP overgrowth. Both QWs are characterized by an indirect band gap. The band alignment in the QWs is identified as type I. In spite of the long (up to milliseconds) exciton lifetimes in the QWs in combination with the electron g factor of +2, the emission of the QWs demonstrates a low circular polarization degree in longitudinal magnetic fields as strong as 10 T. We demonstrate that the electron spin polarization in the Ga(Sb,P)/GaP heterostructure subject to a magnetic field occurs in the GaP layer, and spin-polarized charge carriers captured in the QWs store their spin orientation up to the millisecond time range, indicating very long spin relaxation times for the strongly localized electrons in the Ga(Sb,P)/GaP QWs.