Anatoly Melnikov

Anatoly Melnikov

he/him

Senior Researcher

News

New paper published in J. Open Res. Softw.

Published:

Our article, “Atomize: A Modular Software for Control and Automation of Scientific and Industrial Instruments” was published online today, 07-11-2025, in Journal of Open Research Software. Check it out.
Atomize is a modular software designed to control a wide range of scientific and industrial instruments, integrate them into a unified multifunctional setup, and automate routine experimental work. The software consists of a collection of Python libraries for different apparatus and general-purpose functions, including user-friendly functions for data visualization and storage. All of this, combined with a graphical user interface and the possibility of performing test runs to check the logic of the experiment without access to the devices used, provides a high degree of flexibility and usability, even without significant programming experience. Atomize is freely available on GitHub, and we encourage researchers, engineers, students, and developers working in any field of science and technology to use it in their work.

New paper published in J. Chem. Phys.

Published:

Our article, “Application of pulsed heating in time-resolved EPR spectroscopy for longitudinal relaxation measurements” was published online today, 25-10-2025, in The Journal of Chemical Physics as featured article. Check it out.
Transient or time-resolved electron paramagnetic resonance spectroscopy (TR EPR) is a powerful method for studying various photogenerated paramagnetic species. The use of low-energy quanta, such as terahertz (THz) radiation, as an external stimulus in TR EPR allows the initiation of spin dynamics without generating new paramagnetic species other than those already present in the system. This spin dynamic reflects the return of the system to thermodynamic equilibrium, governed by a spin–lattice relaxation time, T1. The latter, together with a phase memory time, is of paramount importance for the practical implementation of single-molecule magnets and molecular spin qubits. In this work, we present TR EPR spectroscopy with pulsed heating by THz pulses as a versatile spectroscopic method for determining T1 in a wide range of paramagnetic systems. To define the scope of the method, we developed a numerical model based on the Liouville–von Neumann equation, with the equilibrium density matrix defined by the temperature profile of the lattice. Using experimental data obtained for [CoTp2] (cobalt(II) bis[tris(pyrazolyl)borate]) with S = 3/2, we compared the proposed method with two other commonly used techniques: alternating current (AC) magnetometry and pulsed EPR. All three methods were found to be in qualitative agreement and provided complementary information about the relaxation properties. TR EPR spectroscopy showed the orientation dependence of T1. AC magnetometry revealed the dependence of T1 on the value of the external magnetic field, which was attributed in the literature to a field-induced Raman process. Finally, pulsed EPR spectroscopy was found to be biased by strong spectral diffusion.

New paper published in Angew. Chem. Int. Ed.

Published:

Our article, “Thermomagnetic Bistability, Colossal Negative Thermal Expansion, and THz-Heat-Induced Switching in Cu-Nitroxide Complex” was published online today, 08-10-2025, in Angewandte Chemie International Edition. Check it out.
Bistability in molecule-based magnets is crucial for their applications in functional devices, and thermally induced excited spin state trapping (TIESST) represents a promising route to maintain two distinct spin states for a significant period of time. Heterospin compounds based on Cu(II) and nitroxide radicals demonstrate highly tunable non-classical spin transitions, nevertheless they did not reveal TIESST effects up to date. Here, we report the first Cu(II)-nitroxide complex that exhibits TIESST-driven bistability up to 116 K. The TIESST temperature is close to temperatures of the spin transition, which is accompanied by a hysteresis of 30 K (T1/2↑ = 144 K, T1/2↓ = 114 K). The trapped excited state features a very slow relaxation that exceeds 9 h at 95 K. Fast switching is also feasible for this complex: almost complete conversion from the ground to excited state occurs in a single THz pulse within 50 ms. The slow relaxation and preservation of the crystal quality enabled us to perform an XRD study and demonstrate that the trapped and stable phases coexist during the transition. It was demonstrated, that relaxation of excited state proceeds via an autocatalytic mechanism, previously unreported for spin-crossover systems, which introduces a new paradigm in spin relaxation dynamics.

New paper published in Appl. Magn. Res.

Published:

Our article, Monitoring S = 0 ↔ S = 2 Spin-State Switching in Fe(II) Complex Using FT EPR and Trityl Radical as Local Magnetic Field Sensor” was published online today, 02-10-2025, in Applied Magnetic Resonance. Check it out.
The use of EPR spectroscopy for studying spin crossover (SCO) is often limited due to the fact that a large number of complexes do not have an EPR signal in X- and Q-bands. At the same time, EPR spectroscopy, being insensitive to diamagnetic impurities and having excellent sensitivity to paramagnetic centers, provides unique advantages compared to direct current magnetometry. In this paper, we propose a method for detecting the thermal spin transition in a spin crossover Fe(II)-based complex by pulsed EPR in the direct dimension with a specially designed spin-probe. The spin probe is non-contact and reusable, consisting of an ampoule of 1 mm diameter filled with a Finland triarylmethyl radical. To detect the SCO transition, the probe is surrounded by a powder of the SCO complex under investigation. In such a design, the transition can be observed through the shift of the line in the EPR spectrum of the spin probe. The latter occurs due to an addition to the external magnetic field of the spectrometer caused by the transition of the spin crossover complex to a high-spin state, in which it demonstrates paramagnetic properties. The experimental results showed that the proposed method allows one to register a transition in [FeL2][BF4]2 complex, where L is 2,6-di(pyrazol-1-yl)pyridine, in the temperature range of 260–262 K with a 2 K wide hysteresis. The change in the local magnetic field at the location of the spin probe of about 0.004 mT was registered, which is in agreement with the numerical calculations performed.

New paper published in J. Appl. Phys.

Published:

Our article, “Inter-Kramers electric quadrupole transitions in high-spin systems induced by resonant alternating inhomogeneous electric field” was published online today, 24-09-2025, in The Journal of Applied Physics (Vol.138, Issue 12). Check it out.
This study presents a theoretical analysis of the interaction of high-spin systems with inhomogeneous alternating electric field and homogeneous alternating magnetic field that induce electric quadrupole (QT, E2) and magnetic dipole transitions (MT, M1), respectively. In order to distinguish QTs from MTs, an analytical expression for the intensities and selection rules for a model system with a half-integer total spin S = 3/2 was derived using the spin Hamiltonian and operator-equivalent approaches. The direct comparison of the absorption patterns for the QT and MT of a model high-spin Co(II) system was performed in a frequency domain corresponding to Frequency Domain Fourier Transform Terahertz Electron Paramagnetic Resonance spectroscopy. This type of systems often exhibits the properties of a single molecular magnet at helium temperatures and is characterized by a large zero field splitting. Despite more flexible selection rules for electric quadrupole transitions, the powder spectra of QT and MT were shown to be similar, emphasizing the need for precise spectral measurements to determine the dominant transition type in high-spin systems. The approach developed in the paper not only solves a rather complex quantum mechanical problem that includes the estimation of the quadrupole moment of unpaired electrons, but also demonstrates a possible way for advanced manipulation of spin states, a capability crucial for the development of quantum computing and information storage technologies.