Applied Magnetic Resonance最新文献

We have developed a magnetic resonance equipment for low temperature and high magnetic fields, aiming at Dynamic Nuclear Polarization-Nuclear Magnetic Resonance (DNP-NMR) and Electron-Nuclear DOuble Resonance (ENDOR) of diluted spin system using with electron spin resonance (ESR). In this study, we developed a cylindrical resonator with a submicron-thick gold film for millimeter-wave band ESR/NMR double magnetic resonance by exploiting the frequency dependence of the skin depth. ESR measurements were performed using the fabricated resonator at approximately 130 GHz and in the temperature range of 3–70 K of BDPA diluted to 100 mM in polystyrene. ESR sensitivity was obtained from the measurements. The ¹⁹F-NMR signal from the sample holder was also successfully observed.

Terahertz electron spin resonance (THz ESR) measurements of the S = 1/2 frustrated J₁–J₂ chain material NaCuMoO₄(OH) were conducted on a quasi-single-crystal (QSC) sample in a pulsed high magnetic field. The QSC sample was fabricated by modulating the rotation of powder sample in a static magnetic field, resulting in three-dimensional alignment. This paper presents the fabrication method for the QSC sample which was confirmed by the Laue pattern obtained by X-ray diffraction, and the degree of orientation indicated by the anisotropic spectrum of ESR. The THz ESR measurements on the QSC sample of NaCuMoO₄(OH) were performed from 0.06 to 1.56 THz, and we observed ESR spectra for the single axis (b-axis) above the saturation field. We demonstrate that the fabrication of magnetically aligned samples allows the observation of sharp single-axis absorption, even in the THz ESR range, which is challenging for a powder samples with a broad linewidth. Furthermore, we establish that this method is an effective approach for investigating magnetic anisotropy, even in antiferromagnetic powder samples.

We report electron spin resonance studies of double perovskite Ba(_2)CoWO(_6) single crystals. Above (T_textrm{N} = 14) K, we observe a paramagnetic resonance with (g_textrm{eff}simeq 3.66). Upon cooling, this mode transforms into a broad antiferromagnetic resonance (AFMR) with a zero-field energy gap of about 200 GHz. The AFMR becomes barely detectable at low magnetic fields, indicating unusually strong decay processes. We argue that symmetry-allowed anisotropic spin–spin interactions are a possible reason for the pronounced spin-wave damping. Linear spin-wave theory calculations support this scenario.

Following our recent study, the current work performed to explore and elucidate the impacts of the length/angle of hydrogen bonds (H-bonds) of N–H···O/C–H···O type and the percentage s-character of the σ*_N–H/σ*_C–H antibonds partner in the charge transfer (CT) interactions on the nuclear shielding, anisotropy, quadrupole coupling constant, and asymmetry parameters of the imide, amide, carboxamide, and annular nitrogens/methine, methylene, and methyl carbons in the interacting inhibitor–residue pairs in capuramycin, carbacaprazamycin, 3ʹ-hydroxymureidomycin A, and muraymycin D2 binding pockets of MraY_AA–inhibitor complexes (labeled as the QM models I–IV). The cited parameters were calculated at the M06-2X/6-31G** level by including the solvent effects using the polarizable continuum model. In the cases of the imide, amide, carboxamide, and annular nitrogens, the results outlined that a reduction in the H-bond length and an increase in s-character of the N hybrid in the σ*_N–H antibond are associated with a decrease in the ¹⁵N nuclear shielding as well as in the ¹⁴N quadrupole coupling constant but with an enhancement in the ¹⁵N anisotropy and also in the ¹⁴N asymmetry parameter. The similar trends were observed for the nuclear shielding–length, nuclear shielding–s-character, anisotropy–length, anisotropy–s-character correlations of the methine, methylene, and methyl carbons. In addition, when the angles of C–H···O H-bonds are close to 180°, the ¹³C anisotropies increase, while the ¹³C nuclear shieldings decrease. The information obtained here has an immense impact on predicting the behavior of the ¹⁵N/¹³C chemical shifts with the H-bonding characteristics in the protein–ligand complexes.

We review the high field ESR study on the spin S = 1/2 quasi one-dimensional (1D) antiferromagnet with Ising-like anisotropy (hbox {BaCo}_{textrm{2}}hbox {V}_{textrm{2}}hbox {O}_{textrm{8}}). The S = 1/2 Ising-like 1D antiferromagnet is one of the most simple examples of the strongly correlated quantum many body system. In the longitudinal magnetic field along the Ising axis, it exhibits field-induced quantum phase transition from the Néel ordered to the quantum critical Tomonaga-Luttinger liquid (TLL) state with unconventional magnetic excitation. Owing to the moderately low transition field (H_{textrm{c}}) = 3.9 T, the TLL physics can be investigated in detail in (hbox {BaCo}_{textrm{2}}hbox {V}_{textrm{2}}hbox {O}_{textrm{8}}) by means of various experimental probes. The high field ESR measurements in the terahertz region contribute to reveal the low temperature magnetism in this compound via observation of the magnetic excitation in wide frequency and magnetic field regions.

High-spin centers in hexagonal boron nitride are of interest for quantum applications due to their optical and coherent properties. In this work, the behavior of the hyperfine and quadrupole interaction parameters of the negatively charged boron vacancy ((V^{-}_{B})) with nitrogen nuclei in the first and third coordination shells has been investigated using high-frequency (94 GHz, W-band) double electron–nuclear resonance (ENDOR) spectroscopy over a wide temperature range (25–200 K). The ENDOR frequencies governed by the nuclear quadrupole interaction remain nearly constant across the investigated temperature range. This effect is crucial for implementing quantum algorithms involving selective resonant excitation of specific transitions that remain temperature stable. Furthermore, it enables the development of temperature-dependent models for spin-Hamiltonian parameters of the (V_{B}^{-})-center, which are of fundamental importance.

MgMn(_{6})Sn(_{6}) is the itinerant ferromagnet on the kagome lattice with high ordering temperature featuring complex electronic properties due to the nontrivial topological electronic band structure where the spin–orbit coupling (SOC) plays a crucial role. Here, we report a detailed ferromagnetic resonance (FMR) spectroscopic study of MgMn(_{6})Sn(_{6}) aimed to elucidate and quantify the intrinsic magnetocrystalline anisotropy that is responsible for the alignment of the Mn magnetic moments in the kagome plane. By analyzing the frequency, magnetic field, and temperature dependences of the FMR modes, we have quantified the magnetocrystalline anisotropy energy density that reaches the value of approximately (3.5cdot 10^{6}) erg/cm(^{3}) at (T = 3) K and reduces to about (1cdot 10^{6}) erg/cm(^{3}) at (T = 300) K. The revealed significantly strong magnetic anisotropy suggests a sizable contribution of the orbital magnetic moment to the spin magnetic moment of Mn, supporting the scenario of the essential role of SOC for the nontrivial electronic properties of MgMn(_{6})Sn(_{6}).

In many fields—molecular biology, medicine, and chemistry—it is important to determine molecular translational mobility and the rate of the spin exchange in bimolecular collisions. This problem can be studied using spin probes and EPR (electron paramagnetic resonance) spectroscopy. Over the years, the widespread model of spin exchange in dilute solutions that is accepted by the majority of the scientific community has been challenged by a number of theoretical and experimental observations. To answer these challenges, I proposed the new paradigm of the spin exchange of paramagnetic particles and their manifestation in EPR spectroscopy of dilute solutions of paramagnetic particles in 2019. Since then, various experiments have been conducted to validate the fundamental principles of the new spin exchange paradigm. In this article, I provide further development of the new paradigm of spin exchange based on experimental confirmation of key predictions including: non-equivalent spin exchange, contribution of dipole–dipole interaction to the coherence transfer, spin polariton appearance, formation of collective modes of partial magnetizations motion, and provide a new interpretation of the effect of exchange narrowing of the spectrum at high rate of spin coherence transfer. One of the most significant results is that each collective mode gives its own resonance line, and these resonance lines in the case of relatively slow transfer of spin coherence from the interaction partner have a mixed shape. It is important to notice that the formation of collective modes of motion applies to any other spectroscopy where decoherence (relaxation) occurs as a result of stationary spectral diffusion.