Papers by Nikolai Baranov
High Pressure Research, 2003
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Journal of Applied Physics, 1997
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Journal of Alloys and Compounds
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Solid State Sciences, 2013
The transition metal sulfide Fe 4 Ti 3 S 8 with 7:8 composition has been synthesized and studied ... more The transition metal sulfide Fe 4 Ti 3 S 8 with 7:8 composition has been synthesized and studied by using X-ray diffraction, magnetization and electrical resistivity measurements. This compound exhibits a monoclinic crystal lattice (space group I12/m1). The substitution of Ti for Fe in Fe 7 S 8 is found to result in a lowering of the Curie temperature (T C z 205 K), in a larger value of the coercive field (H c w 9 kOe at low temperatures) and in a substantial growth of the resultant magnetic moment per formula unit (m FU) in comparison with Fe 7 S 8. An enhanced value of m FU is attributed to the preferential substitution of Ti in alternating cation layers. From the paramagnetic susceptibility measured within temperature interval (250e350) K, a reduced value of the effective moment per iron (m Fe w 2.4m B) was determined. The electrical resistivity of Fe 4 Ti 3 S 8 shows a non-metallic behavior and is affected by magnetic ordering.
Physics of the Solid State, 2013
The electrical properties of intercalated Ag x HfSe 2 compounds (x = 0.1, 0.2) have been investi ... more The electrical properties of intercalated Ag x HfSe 2 compounds (x = 0.1, 0.2) have been investi gated for the first time. Investigations have been performed using various current electrodes, which make it possible to pass either the electron current or the ion current across the sample. Polarization effects, which indicate the self consistent migration of charge carriers in the samples, have been found for the samples at room temperature. Based on the characteristic features of polarization decay, coefficients of conjugated chemical diffusion have been evaluated.
Physical Review B, 2006
Quantum dissipation theory of slow magnetic relaxation mediated by domain-wall motion in one-dime... more Quantum dissipation theory of slow magnetic relaxation mediated by domain-wall motion in one-dimensional chain compound [Mn(hfac) 2 BNO H ].
Physical Review B, 2007
Measurements of the specific heat have been performed on Gd 1−x Y x Ni 2 ͑x =0,0.2͒ compounds and... more Measurements of the specific heat have been performed on Gd 1−x Y x Ni 2 ͑x =0,0.2͒ compounds and their nonmagnetic analogs Lu 1−y Y y Ni 2 , which have similar molar masses. It is found that the difference between the entropies of magnetic and nonmagnetic compounds with identical molar masses surpasses substantially ͑by 14-19%͒ the theoretical limit for the magnetic contribution S m = ͑1−x͒R ln͑8͒ calculated assuming that only Gd ions possess a magnetic moment. This observed enhancement of the magnetic entropy in Gd 1−x Y x Ni 2 is believed to result from spin fluctuations induced by f-d exchange in the 3d electron subsystem of Ni.
Physical Review B, 2006
The substitution of Tb for Tm in the Laves phase compound TmCo 2 leads to appearance of a magneti... more The substitution of Tb for Tm in the Laves phase compound TmCo 2 leads to appearance of a magnetic moment on the Co atoms through the metamagnetic transition in the itinerant d-electron subsystem and gives rise to long-range ferrimagnetic order in Tm 1−x Tb x Co 2 at x ജ 0.15. The magnetic state of the compound Tm 0.9 Tb 0.1 Co 2 , i.e., just below the critical Tb concentration, is characterized by the presence of large regions with short-range magnetic order and localized spin fluctuations ͑LSFs͒ induced in the Co 3d-electron subsystem by the fluctuating f-d exchange due to the Tm-Tb substitution. The peculiar magnetic state of this compound is strongly influenced by an external magnetic field which produces a first-order magnetic phase transition to a long-range ferrimagnetic state with the magnetic moment on the Co atoms up to ͑0.7-0.8͒ B. This field-induced transition in Tm 0.9 Tb 0.1 Co 2 is found to be irreversible. It is accompanied by a giant and irreversible reduction of the electrical resistivity ͑⌬ / ϳ −45% ͒, specific heat ͑by about 3.7 times at 2 K͒, and intensity of magnetic neutron scattering. Such behavior is associated with the field-induced metamagnetic transition in the itinerant d-electron subsystem mediated by the f-d exchange. Significantly enhanced values of the residual resistivity and the coefficient ␥ of the T-linear contribution to the specific heat in the compound with x = 0.1 as well as their unusual behavior with temperature and under application of the magnetic field is ascribed to the presence of LSF.
Physical Review B, 2013
Contrary to previous studies that identified the ground state crystal structure of the entire R3C... more Contrary to previous studies that identified the ground state crystal structure of the entire R3Co series (R is a rare earth) as orthorhombic P nma, we show that Y3Co undergoes a structural phase transition at Tt ≃ 160 K. Single crystal neutron diffraction data reveal that at Tt 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 P nma structure of Y3Co. In particular, a transversal acoustic phonon mode along the (00ξ) direction has imaginary frequencies at ξ < 1/4. Employing inelastic neutron scattering measurements we find a strong damping of the (00ξ) phonon mode below a critical temperature Tt. 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 Y3Co as a system with the charge density wave instability.
Physica B: Condensed Matter, 2002
The Er 3 Co compound with orthorhombic crystal structure has been investigated by means of magnet... more The Er 3 Co compound with orthorhombic crystal structure has been investigated by means of magnetic susceptibility, magnetization, electrical resistivity and heat capacity measurements which were made for the first time on single crystalline samples. Below 13.8 K this compound exhibits a complex noncollinear ferromagnetic structure which results from the low symmetry crystalline electric field that surpasses the exchange interaction. Using the magnetization and magnetoresistance measurements along the main crystallographic directions, a complicated and anisotropic magnetization process was revealed. The variation of the electrical resistivity of Er 3 Co with the temperature is discussed assuming an influence of spin fluctuations rising from f2d exchange interactions.
Physical Review B - PHYS REV B, 2007
Measurements of the specific heat have been performed on Gd1-xYxNi2 (x=0,0.2) compounds and their... more Measurements of the specific heat have been performed on Gd1-xYxNi2 (x=0,0.2) compounds and their nonmagnetic analogs Lu1-yYyNi2 , which have similar molar masses. It is found that the difference between the entropies of magnetic and nonmagnetic compounds with identical molar masses surpasses substantially (by 14-19%) the theoretical limit for the magnetic contribution Sm=(1-x)Rln(8) calculated assuming that only Gd ions possess a magnetic moment. This observed enhancement of the magnetic entropy in Gd1-xYxNi2 is believed to result from spin fluctuations induced by f-d exchange in the 3d electron subsystem of Ni.
Journal of the American Chemical Society, 2007
Figure 2S. Inter-and intrachain Co-Co distances (Å).
Journal of Physics: Condensed Matter, 2013
Measurements of the magnetic susceptibility, magnetization, electrical resistivity and neutron di... more Measurements of the magnetic susceptibility, magnetization, electrical resistivity and neutron diffraction have been performed for the compound Fe(0.5)TiS(2) in which Fe atoms are intercalated between S-Ti-S tri-layers. It has been shown that this compound with a monoclinic crystal structure exhibits an antiferromagnetic (AF) ground state below the Néel temperature T(N) ≈ 140 K. Small deviations from the stoichiometry and some disordering effects caused by the additional low-temperature heat treatment do not affect substantially the AF state in Fe(0.5)TiS(2). According to neutron diffraction data the magnetic structure at 2 K is described by the propagation vector k = (1/4,0,1/4). The Fe magnetic moments with a value of (2.9 ± 0.1) μ(B) are directed at an angle of (78.5 ± 1.8)° to the layers. Application of the magnetic field at T &lt; T(N) induces a metamagnetic phase transition to the ferromagnetic (F) state, which is accompanied by the large magnetoresistance effect (|Δρ/ρ| up to 27%). Below 100 K, the field-induced AF-F transition is found to be irreversible, as evidenced by magnetoresistance and neutron diffraction measurements. The magnetization reversal in the metastable F state is accompanied at low temperatures by substantial hysteresis (ΔH ~ 100 kOe) which is associated with the Ising character of Fe ions.
Journal of Physics: Condensed Matter, 2005
The results of crystal structure, bulk magnetic properties and magnetic structure investigations ... more The results of crystal structure, bulk magnetic properties and magnetic structure investigations are reported for the intercalated compound Cr 0.5 TiSe 2. The Cr atoms are found to be ordered in the hexagonal TiSe 2 matrix forming a superlattice a = a √ 3, b = a , c = 2c. The first neutron diffraction measurements performed for this compound together with susceptibility and magnetization data have shown that this compound exhibits a complex incommensurate magnetic structure below T N = 42 K. This structure is suggested to arise from the competition between the ferromagnetic exchange interaction dominating mainly within the Cr layers and antiferromagnetic interlayer exchange. Because of weakness of the interlayer exchange in comparison with intralayer one this compound exhibits metamagnetic properties.
Journal of Magnetism and Magnetic Materials, 1983
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Journal of Physics-condensed Matter - J PHYS-CONDENS MATTER, 2005
The real-space renormalization group approach is applied to study critical temperatures of a syst... more The real-space renormalization group approach is applied to study critical temperatures of a system consisting of interacting spin chains of spin S = 1, with an inner antiferromagnetic exchange, which form a honeycomb crystal lattice. Using the anisotropic Heisenberg model we calculate the critical temperature as a function of the anisotropic parameter and the ratio of the interchain and intrachain interactions. A comparison our results with those obtained from RSRG calculations for the same model of spin-1/2 on a square lattice is given.
Journal of Alloys and Compounds, 1992
In the quasi-binary intermetallic compound Ero.55Y0.45Co2, an irreversible change of 44% in the c... more In the quasi-binary intermetallic compound Ero.55Y0.45Co2, an irreversible change of 44% in the coefficient of the linear terra of the low-temperature specific heat T is observed in zero field after application of a 5 T magnetic field in addition to the change in the electrical resistivity and unit cell volume. The decrease of T is attributed not only to the decrease in density of the electronic states, but also to the suppression of spin fluctuations.
Journal of Alloys and Compounds, 2004
Using the measurements of the magnetic susceptibility and magnetization we have investigated the ... more Using the measurements of the magnetic susceptibility and magnetization we have investigated the magnetic properties of Mn-intercalated Mn x TiSe 2 compounds having a hexagonal crystal structure of a quasi-two-dimensional type. Unlike other 3d-transition metals, intercalation of Mn ions between Se-Ti-Se tri-layers increases the c-parameter of the lattice. All compounds of Mn x TiSe 2 exhibit a paramagnetic behavior above ∼15 K. The effective magnetic moment µ eff of Mn in Mn x TiSe 2 is found to be less than µ eff for the free Mn 2+ ion. In a low-temperature region a spin-glass or cluster-glass behavior depending on the intercalant concentration is observed. The paramagnetic Curie temperature θ p takes negative values and decreases monotonically with increasing x, while the freezing temperature shows non-monotonous change at the intercalation. The obtained results are discussed taking into account Mn 3d-Ti 3d hybridization effects and variations of intralayer and interlayer exchange interactions with intercalation.
Journal of Alloys and Compounds, 1994
... 40. Beckman and L. Lundgren, Compounds of transition elements with nonmetals, in KHJ Buschow ... more ... 40. Beckman and L. Lundgren, Compounds of transition elements with nonmetals, in KHJ Buschow (ed.), Handbook of Magnetic Materials, Vol. 6, Elsevier Science Publishers, 1991, Chapter 3, p. 181. 5 C. Kittel, Phys. Rev., 120 (1960) 335. 6 RB Flippen and FJ Darnell, J. Appl. ...
The European Physical Journal B, 2009
Motivated by recent experimental results reporting giant coercive fields in Co(II)based molecular... more 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.
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Papers by Nikolai Baranov