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M. R. Gafurov

Publications and source records attributed to M. R. Gafurov.

14 recordsLinked to original sources
arXiv2025

Ce(III) Ions in Hydroxyapatite: Nanoscale Environment Investigation

This paper presents a comprehensive study of cerium-doped hydroxyapatite (Ce-HAp), a material of interest for biomedical applications due to the good biocompatibility of hydroxyapatite and the antioxidant activity of cerium ions. We employ advanced electron paramagnetic resonance (EPR) techniques, including continuous wave (CW) and pulsed X-band experiments, electron spin echo envelope modulation (ESEEM), and electron-electron double resonance (ELDOR)-detected NMR (EDNMR) to investigate the local coordination and electron environment of cerium ions in the hydroxyapatite matrix. The experimental results are complemented by g-tensor calculation, which allows us to interpret the EPR spectra and identify the types of paramagnetic centers. Our results show that during the synthesis of hydroxyapatite powder by the chemical precipitation method using nitrates, cerium ions enter the structure mainly in the trivalent state and replace calcium ions in two nonequivalent positions. In addition to cerium ions, nitrate radicals are found in the HAp structure. Heat treatment reduces the amount of nitrate radicals and increases crystallinity. This work expands the understanding of the role of cerium in calcium phosphates and provides a methodological basis for the characterization of doped bioceramics using various EPR approaches.

cond-mat.mtrl-sci↗
arXiv2025

Probing Remote Nuclear Magnetic Moments in hBN with VB Electron Spin

Since the initial discovery of optically addressable spins of the negatively charged boron vacancy defect (VB) in hexagonal boron nitride (hBN), substantial progress has been made, enabling promising applications in quantum sensing, information processing, and simulations. A deep understanding of the VB (electron): hBN (nuclear) spin systems is crucial for realizing these potentials. In this article, we employ Electron Nuclear Double Resonance (ENDOR) to demonstrate the sensing of dis tant nuclear spins via the VB electron spin. We identify the nature and localization of the probed nuclear magnetic moments as 14N spins localized 0.4 nm away from the vacancy and resolve the energies of the corresponding interactions. Density Functional Theory (DFT) calculations further confirm these findings, providing a detailed description of the interactions between the VB electron spin and surrounding nitrogen atoms in different shells. The results establish the VB electron spin as a promising tool for developing novel van der Waals material-based nuclear magnetic resonance (NMR) probes, advancing the understanding of spin physics in hBN, and unlocking its potential to study distant nuclear spin interactions in the host.

cond-mat.mtrl-sci↗
arXiv2025

Influence of 14N hyperfine interaction on electron nuclear double resonance of boron vacancy in hexagonal boron nitride

The research focuses on the explanation of a phenomenon observed in the spectra of electron nuclear resonance (ENDOR) pertaining to nitrogen atoms adjacent to the boron vacancy (VB) defect in hexagonal boron nitride (hBN). The phenomenon is manifested as a shift of the ENDOR spectrum lines with respect to the nitrogen Larmor frequency. It is hypothesized that these shifts are indicative of a substantial hyperfine interaction between the VB defect and the 14N nuclei in hBN. A calculation utilizing second-order perturbation theory was executed to determine the positions of the ENDOR spectrum lines, resulting in the formulation of correction equations. The values obtained from the perturbation theory corrections align well with the experimental results. The extent of nuclear state admixture into electron states was found to be around 0.04-0.07%.

cond-mat.mtrl-sci↗
arXiv2024

Optical Spin Initialization of Nitrogen Vacancy Centers in a 28Si-Enriched 6H-SiC Crystal for Quantum Technologies

High-spin defect centers in crystal matrices are used in quantum computing technologies, highly sensitive sensors, and single-photon sources. In this work, optically active nitrogen-vacancy color centers NV in a 28Si-enriched (nuclear spin I = 0) 6H-28SiC crystal have been studied using the photoinduced (980 nm) high-frequency (94 GHz, 3.4 T) pulsed electron paramagnetic resonance method at a temperature of 150 K. Three structurally nonequivalent types of NV- centers with axial symmetry have been identified and their spectroscopic parameters have been determined. Long spin-lattice, T1=1.3 ms, and spin-spin, T2=59 us, ensemble relaxation times of NV- centers with extremely narrow (450 kHz) absorption lines allow highly selective excitation of resonant transitions between sublevels caused by the weak hyperfine interaction (A = 1 MHz) with 14N (I = 1) nuclei for the quantum manipulation of the electron spin magnetization.

cond-mat.mtrl-sci↗
arXiv2020

Coherence times of Ce$^{3+}$ spin states in CaWO$_{4}$ crystal

We study the coherence times and perform manipulations on the lowest-energy states of trivalent cerium ion in calcium tungstate crystal. We find the phase memory time reaching 14.2 $μ$s and the time of coherent manipulations reaching 0.3 $μ$s in the low-temperature limit, the latter can potentially be elongated by using the rotation angle and off-resonance error correction schemes.

cond-mat.mes-hall↗
arXiv2017

Superhyperfine interactions in Ce3+ doped LiYF4 crystal: ENDOR measurements

The first observation of the resolved Mims electron-nuclear double resonance (ENDOR) spectra from the nearby and remote nuclei of 19F and 7Li nuclei on impurity Ce3+ ions in LiYF4 crystal is reported. It shows that LiYF4:Ce3+ system can be exploited as a convenient matrix for performing spin manipulations and adjusting quantum computation protocols while ENDOR technique could be used for the investigation of electron-nuclear interaction with all the nuclei of the system and exploited for the electron-nuclear spin manipulations.

cond-mat.mtrl-sci↗
arXiv2016

Coherent spin dynamics in gadolinium-doped CaWO4 crystal

We report the first observation of Rabi oscillations in the spin-7/2 ensemble of trivalent gadolinium ions hosted in CaWO$_4$ single crystal. A number of transitions within the lowest electronic multiplet $^8S_{7/2}$ of Gd$^{3+}$ ion are studied using a combination of continuous-wave and pulsed electron paramagnetic resonance spectroscopy. The corresponding Rabi damping curves and the spin coherence times are detected at varying strengths of the microwave field. These data are well reproduced by a theoretical model which accounts for the intrinsic inhomogeneity of the microwave field within the microwave resonator and the magnetic dipole interactions in the diluted spin ensemble. The results indicate that the studied 8-level ground manifold of Gd$^{3+}$ ion can represent an effective three qubit quantum system.

cond-mat.mes-hall↗
arXiv2014

Coherent manipulation of dipolar coupled spins in an anisotropic environment

We study coherent dynamics in a system of dipolar coupled spin qubits diluted in solid and subjected to a driving microwave field. In the case of rare earth ions, anisotropic crystal background results in anisotropic g tensor and thus modifies the dipolar coupling. We develop a microscopic theory of spin relaxation in transient regime for the frequently encountered case of axially symmetric crystal field. The calculated decoherence rate is nonlinear in Rabi frequency. We show that the direction of static magnetic field that corresponds to the highest spin g-factor is preferable in order to obtain higher number of coherent qubit operations. The results of calculations are in excellent agreement with our experimental data on Rabi oscillations recorded for a series of CaWO4 crystals with different concentrations of Nd3+ ions.

cond-mat.mes-hall↗
arXiv2005

Temperature dependence of the EPR linewidth of Yb3+ - ions in Y0.99Yb0.01Ba2Cu3OX compounds: Evidence for an anomaly near TC

Electron paramagnetic resonance experiments on doped Yb3+ ions in YBaCuO compounds with different oxygen contents have been made. We have observed the strong temperature dependence of the EPR linewidth in the all investigated samples caused by the Raman processes of spin-lattice relaxation. The spin-lattice relaxation rate anomaly revealed near TC in the superconducting species can be assigned to the phonon density spectrum changes

cond-mat.supr-con↗
arXiv2005

Electron Spin-Lattice Relaxation of doped Yb3+ ions in YBa2Cu3Ox

The electron spin-lattice relaxation (SLR) times T1 of Yb3+‡ ions were measured from the temperature dependence of electron spin resonance linewidth in Y0.99Yb0.01Ba2Cu3Ox with different oxygen contents. Raman relaxation processes dominate the electron SLR. Derived from the temperature dependence of the SLR rate, the Debye temperature (Td) increases with the critical temperature Tc and oxygen content x. Keywords: EPR; ESR; Electron spin-lattice relaxation; Debye temperature; Critical temperature

cond-mat.supr-con↗
arXiv2005

Electron Spin-Lattice Relaxation of Er3+ ions in Er0.01Y0.99Ba2Cu3Ox

The temperature dependence of the electron spin-lattice relaxation SLR was studied in Er0.01Y0.99Ba2Cu3Ox compounds. The data derived from the electron spin resonance ESR and SLR measurements were compared to those from inelastic neutron scattering studies. SLR of Er3+ ions in the temperature range from 20 K to 65 K can be explained by the resonant phonon relaxation process with the involvement of the lowest excited crystalline-electric-field electronic states of Er3+. These results are consistent with a local phase separation effects. Possible mechanisms of the ESR line broadening at lower temperatures are discussed. Keywords: YBCO; EPR; ESR; Electron spin-lattice relaxation time, T ; Crystalline-electric-field

cond-mat.supr-con↗
arXiv2004

EPR study of some rare-earth ions (Dy3+, Tb3+ and Nd3+) in YBa2Cu3O6 compound

We investigate the low temperature X-band electron paramagnetic resonance (EPR) of YBa2Cu3O6 compounds with x = 6.0 doped with Dy3+, Tb3+, and Nd3+. The EPR spectra of Dy3+ and Tb3+ have been identified. The EPR of Tb3+ is used also to study the effect of suppression of high Tc superconductivity. The EPR of Nd3+ is probably masked by the intense resonance of Cu2+. All experimental EPR results compare well with theoretical estimations.

cond-mat.supr-con↗