arXiv subjects

N. V. Baranov

Publications and source records attributed to N. V. Baranov.

6 recordsLinked to original sources

arXiv2017

Suppression of magnetism under pressure in FeS: a LDA+DMFT study

We show that evolution of magnetic properties in FeS under pressure cannot be explained only in terms of a spin state transition. While uniform compression does show substantial suppression of the local magnetic moment and increase of the weights of configurations with low spin, analysis of the local spin-spin correlation function demonstrates increase of the spin itinerancy. This is related to a strong modification of the electronic structure under pressure: in the high-pressure phase FeS is in the Fermi-liquid state, while decrease of the pressure moves the system to an orbital-selective regime.

cond-mat.str-el↗

arXiv2013

Temperature-driven Phase Transformation in Y_3Co: Neutron Scattering and First-principles Studies

Contrary to previous studies that identified the ground state crystal structure of the entire R_3Co series (R is a rare earth) as orthorhombic Pnma, we show that Y_3Co undergoes a structural phase transition at T_t=160K. Single crystal neutron diffraction data reveal that at T_t the trigonal prisms formed by a cobalt atom and its six nearest-neighbor yttrium atoms experience distortions accompanied by notable changes of the Y-Co distances. The formation of the low-temperature phase is accompanied by a pronounced lattice distortion and anomalies seen in heat capacity and resistivity measurements. Density functional theory calculations reveal a dynamical instability of the Pnma structure of Y_3Co. In particular, a transversal acoustic phonon mode along the (00z) direction has imaginary frequencies at z<1/4. Employing inelastic neutron scattering measurements we find a strong damping of the (00z) phonon mode below a critical temperature T_t. The observed structural transformation causes the reduction of dimensionality of electronic bands and decreases the electronic density of states at the Fermi level that identifies Y_3Co as a system with the charge density wave instability.

cond-mat.mtrl-sci↗

arXiv2012

Field-induced high coercive ferromagnetic state and magnetoresistance in the antiferromagnetically ordered compound Fe0.5TiS2

The measurements of the magnetic susceptibility, magnetization, electrical resistivity and magnetoresistance have been performed for the Fe intercalated compound Fe0.5TiS2. According to X-ray diffraction measurements the Fe0.5TiS2 compound synthesized in the present work has a monoclinic crystal structure (space group I12/m1) which results from the ordering of Fe ions and vacancies between S-Ti-S tri-layres. The changes in the heat-treatment conditions at temperatures below 1100 Celsius degrees do not lead to an order-disorder transition within the subsystem of intercalated Fe ions. It has been shown that this compound exhibits an antiferromagnetic (AF) ground state below the Neel temperature TN = 140 K. Application of the magnetic field at T < TN induces a metamagnetic phase transition to the ferromagnetic (F) state, which is accompanied by the large magnetoresistance effect (up to 27 %). The field-induced AF-F transition is found to be irreversible below ~ 100 K. The magnetization reversal in the metastable F state at low temperatures is accompanied by substantial hysteresis (~ 100 kOe) which is associated with the Ising character of Fe ions.

cond-mat.mtrl-sci↗

arXiv2009

Magnetic hysteresis in a molecular Ising ferrimagnet: Glauber dynamics approach

Motivated by recent experimental results reporting giant coercive fields in Co(II)-based molecular magnets we present a theory of hysteresis phenomena based on the Glauber stochastic dynamics. Unusual form of hysteresis loops is similar to those of found in Co-based quasi-one-dimensional ferrimagnet CoPhOMe at low temperatures. Temperature dependence of the coercive field has a characteristic form with an inflection that may serve as an indicator of the Glauber dynamics in real compounds. A relevance of the model for other Co-based molecular magnets is discussed.

cond-mat.stat-mech↗

arXiv2006

Quantum dissipation theory of slow magnetic relaxation mediated by domain-wall motion in one-dimensional chain compound [Mn(hfac)_{2}BNO_{H}}]

Based on a quantum dissipation theory of open systems, we present a theoretical study of slow dynamics of magnetization for the ordered state of the new molecule-based magnetic complex [Mn(hfac)_{2}BNO_{H}] composed from antiferromagnetically coupled ferrimagnetic (5/2,1) spin chains. Experimental investigations of the magnetization process in pulsed fields have shown that this compound exhibits a metamagnetic AF-FI transition at a critical field in the order of the interchain coupling. A strong frequency dependence for the ac-susceptibility has been revealed in the vicinity of the AF-FI transition and was associated with an AF-FI interface kink motion. We model these processes by a field-driven domain-wall motion along the field-unfavorable chains correlated with a dissipation effect due to a magnetic system-bath coupling. The calculated longitudinal magnetization has a two-step relaxation after the field is switched off and are found in good agreement with the experiment. The relaxation time determined from the imaginary part of the model ac-susceptibility agrees qualitatively with that found from the remanent magnetization data.

cond-mat.mtrl-sci↗

arXiv2005

Real-space renormalization group study of the anisotropic antiferromagnetic Heisenberg model of spin S=1 on a honeycomb lattice

The real-space RG approach is applied to study critical temperatures of system consisting of interacting spin chains of spin S=1 with an inner antiferromagnetic exchange which form a honeycomb crystal lattice. Using anisotropic Heisenberg model we calculate critical temperature as a function of anisotropic parameter and the ratio of interchain and intrachain interactions. A comparison our results with those obtained from RGRS calculations for the same model of spin-1/2 on a square lattice is given.

cond-mat.str-el↗