Vladimir Markovich - Academia.edu (original) (raw)

Uploads

Papers by Vladimir Markovich

Research paper thumbnail of Meyer-Neldel rule in the conductivity of phase separated manganites

Journal of Electrical Engineering

Meyer-Neldel behaviour of the conductivity of phase separated La1−xCaxMnO3 manganite system in th... more Meyer-Neldel behaviour of the conductivity of phase separated La1−xCaxMnO3 manganite system in the low Ca-doping range has been investigated. Evolution of the isokinetic temperature of the conductivity, modified by Ca-doping, hydrostatic pressure and current bias has been determined. In addition, the evolution of the isokinetic temperature with ageing has also been studied. It is found that the Meyer-Neldel behaviour of the manganite system stems from multi-excitation entropy mechanism. The isokinetic temperatures estimated from pressure and doping effects coincide but differ from those determined using current and ageing controlled conductivity changes. It is concluded that in the presence of a detailed theoretical model of the excitations coupling in manganites, the investigations of the Meyer-Neldel effect may became a powerful tool for characterization and investigation of transport mechanisms in phase separated manganites.

Research paper thumbnail of Suppression of the ferromagnetic-insulating phase in self-dopedLa0.94Mn0.98O3crystals under pressure

Physical Review B

The effect of hydrostatic pressure P on the magnetic and transport properties of self-doped La 0.... more The effect of hydrostatic pressure P on the magnetic and transport properties of self-doped La 0.94 Mn 0.98 O 3 crystals has been investigated at pressures up to 1 GPa and in the temperature range 15ϽTϽ300 K. It was found that the applied pressure enhances the double-exchange coupling, increases the magnetization, and lowers the ferromagnetic-insulator transition temperature. The results obtained here for the self-doped crystals are compared with those observed for lightly doped La 1Ϫx Sr x MnO 3. It is shown that similar mechanisms of ferromagnetic clustering and percolative polarons may account also for the magnetic and transport properties of the self-doped manganites.

Research paper thumbnail of Effect of pressure and magnetic field on the resistance of the self-doped manganese perovskiteLa0.91Mn0.95O3

Physical Review B

The effect of hydrostatic pressure P up to 9 kbar and applied magnetic fields H up to 15 kOe on t... more The effect of hydrostatic pressure P up to 9 kbar and applied magnetic fields H up to 15 kOe on the transport properties of La 0.91 Mn 0.95 O 3 at temperatures Tϭ77-300 K is reported. At ambient pressure and zero magnetic field the transition to a ferromagnetic phase takes place at T c Ϸ252 K whereas a maximum in resistivity is observed at T r ϭ262 K. It is shown that the maximum in the derivative d(T, P)/dT occurs at the ferromagnetic transition temperature T c. The observed pressure coefficient d ln T c /dPϷ0.0048 kbar Ϫ1 is found to be consistent with Mn ϩ4 concentration of about 40%. The observed behavior of the resistivity (T) at applied magnetic field is analyzed by the mean field theory. It is shown that the maximum of d(T)/dT at applied magnetic field H shifts according to H 2/3 .

Research paper thumbnail of Superconducting properties of GdBa2 - xSrxCu3O7 - delta

Physics of the Solid State

Research paper thumbnail of Magnetism of the Gd3 + sublattice in the system GdBa2 - xSrxCu3O7 - delta

Physics of the Solid State

Research paper thumbnail of Low-temperature structural phase transition of the Jahn-Teller type in DyBa2Cu3O7−δ

Physica C Superconductivity

ABSTRACT

Research paper thumbnail of Pressure effect on transport properties of electron-doped Sm0.2Ca0.8Mn1-xRuxO3(x=0 0.04) manganites

Journal of Applied Physics

ABSTRACT

Research paper thumbnail of Conductivity oscillations in current-induced metastable states in low-doped manganite single crystals

Physical Review B, 2002

Deterministic oscillations of current-induced metastable resistivity in changing voltage have bee... more Deterministic oscillations of current-induced metastable resistivity in changing voltage have been detected in La 0.82 Ca 0.18 MnO 3 single crystals. At low temperatures, below the Curie point, application of specific bias procedures switches the crystal into metastable resistivity state characterized by appearance of pronounced reproducible and random structures in the voltage dependence of the differential conductivity. In certain bias range equally spaced broad conductivity peaks have been observed. The oscillating conductivity has been tentatively ascribed to resonances in a quantum well within the double tunnel barrier of intrinsic weak-links associated with twin-like defect boundaries.

Research paper thumbnail of Current-induced metastable resistive states with memory in low-doped manganites

Physical Review B, 2001

... CAS]. DA Shulyatev, AA Arsenov, SG Karabashev, and Ya.M. Mukovskii, J. Cryst. Growth 198/199,... more ... CAS]. DA Shulyatev, AA Arsenov, SG Karabashev, and Ya.M. Mukovskii, J. Cryst. Growth 198/199, 511 (1999) [INSPEC]. ... 1997 . 14 DA Shulyatev, AA Arsenov, SG Karabashev, and Ya.M. Mukovskii, J. Cryst. Growth 198?99, 511 1999 . ...

Research paper thumbnail of Magnetic ordering of Nd3 + in a NdBa2Cu3O6.3 single crystal

Physics of the Solid State

Research paper thumbnail of Oxygen ordering in the system YBa1.5Sr0.5Cu3Ox under pressure

Physics of the Solid State

ABSTRACT

Research paper thumbnail of Anomalous behavior of the paramagnetic susceptibility of GdBaCuO6.2 single crystals in a magnetic field

Physics of the Solid State

Research paper thumbnail of Superconductivity of the high-Tc system Gd1 + xBa2 - xCu3O7 - delta

Research paper thumbnail of Effect of pressure-induced oxygen ordering on the superconducting properties of GdBa2 - ySryCu3Ox

Physics of the Solid State

Research paper thumbnail of Magnetic transformations in single-crystal GdBaCuO6.2 below 20 K. Determination of the spin interactions of Gd3 + ions

Physics of the Solid State

Research paper thumbnail of Dimensional crossover in the diamagnetic behavior of a GdBaCuO single crystal as the oxygen content is varied

Research paper thumbnail of ChemInform Abstract: Magnetic Properties of Perovskite Manganites and Their Modifications

Research paper thumbnail of Pressure effects on the charge-ordering state in Sm 0.2 Ca 0.8 Mn 1 − x Ru x O 3 ( x = 0 , 0.04 )

Physical Review B, 2001

Transport properties of Sm0.2Ca0.8Mn1-xRuxO3 (x=0,0.04) have been investigated in the temperature... more Transport properties of Sm0.2Ca0.8Mn1-xRuxO3 (x=0,0.04) have been investigated in the temperature range 15-300 K in external magnetic fields up to 1.5 T and hydrostatic pressure up to 1 GPa. The 4% Ru doping in Mn site converts the low-temperature robust orbital ordered phase observed in the undoped compound to a two-phase (ferromagnetic and charge ordered) ground state. As a result of such doping (phase-separated ground state), colossal magnetoresistance, slow relaxation of resistivity with logarithmic time dependence, and prehistory effects that are enhanced by pressure are observed in Sm0.2Ca0.8Mn0.96Ru0.04O3. In contrast, the above effects are absent in Sm0.2Ca0.8MnO3.

Research paper thumbnail of Unconventional exchange bias effect driven by phase separation in basically antiferromagnetic Sm0.1Ca0.6Sr0.3MnO3

Journal of Alloys and Compounds, 2015

ABSTRACT Magnetic investigations, focused on the uncommon behavior of the exchange bias (EB) effe... more ABSTRACT Magnetic investigations, focused on the uncommon behavior of the exchange bias (EB) effect, have been performed for basically antiferromagnetic (AFM) electron doped manganite Sm0.1Ca0.6Sr0.3MnO3. The studied system in the ground state exhibits a heterogeneous spin configuration consisting of the C-type antiferromagnetic phase with the Néel temperature TN�C �≈ 150 K, the G-type AFM phase with the Néel temperature TN�G ≈� 70 K, and a FM-like phase with very weak spontaneous magnetic moment. The phase separation, into two different AFM phases and a FM-like phase at the temperatures below TN–G, leads to nusual magnetic properties, such as: narrowing of magnetic hysteresis loops in field cooling process, unconventional EB effect associated with spontaneous magnetization at temperatures below TN–C, strong magnetic field dependence of the negative exchange bias at fields below 100 Oe turning into practically field independent one for fields above 0.5 kOe, significant shift of EB with temperature with a change of the sign from negative at 10 K to positive above 40 K. The atypical magnetic properties are discussed and related to two different interfaces appearing between coexisting magnetic phases.

Research paper thumbnail of FMR probing of ‘spontaneous’ and Ru-doping induced ferromagnetism in Sm0.2Ca0.8Mn1−xRuxO3 (x≤0.08) manganites

Solid State Communications, 2003

The FMR spectra of electron-doped Sm 0.2 Ca 0.8 Mn 12x Ru x O 3 ð0 # x # 0:08Þ system are measure... more The FMR spectra of electron-doped Sm 0.2 Ca 0.8 Mn 12x Ru x O 3 ð0 # x # 0:08Þ system are measured and analyzed in the temperature interval 100 # T # 320 K; including all critical points of magnetic transitions. It is shown that the origin of macroscopic magnetization in the parent Sm 0.2 Ca 0.8 MnO 3 and Ru-doped compounds is essentially different. The bound magnetic polarons formation at temperatures below the Neel point is suggested to be responsible for the appearance of a minute 'spontaneous' magnetic moment in Sm 0.2 Ca 0.8 MnO 3. Doping with Ru induces formation of 'conventional' ferromagnetic phase in antiferromagnetic matrix. Such a phase is characterized by a Curie temperature, which is higher than the Neel temperature of the matrix. Magnetic phase diagrams of Sm 0.2 Ca 0.8 Mn 12x Ru x O 3 determined by ferromagnetic resonance and dc magnetic measurements are discussed.

Research paper thumbnail of Meyer-Neldel rule in the conductivity of phase separated manganites

Journal of Electrical Engineering

Meyer-Neldel behaviour of the conductivity of phase separated La1−xCaxMnO3 manganite system in th... more Meyer-Neldel behaviour of the conductivity of phase separated La1−xCaxMnO3 manganite system in the low Ca-doping range has been investigated. Evolution of the isokinetic temperature of the conductivity, modified by Ca-doping, hydrostatic pressure and current bias has been determined. In addition, the evolution of the isokinetic temperature with ageing has also been studied. It is found that the Meyer-Neldel behaviour of the manganite system stems from multi-excitation entropy mechanism. The isokinetic temperatures estimated from pressure and doping effects coincide but differ from those determined using current and ageing controlled conductivity changes. It is concluded that in the presence of a detailed theoretical model of the excitations coupling in manganites, the investigations of the Meyer-Neldel effect may became a powerful tool for characterization and investigation of transport mechanisms in phase separated manganites.

Research paper thumbnail of Suppression of the ferromagnetic-insulating phase in self-dopedLa0.94Mn0.98O3crystals under pressure

Physical Review B

The effect of hydrostatic pressure P on the magnetic and transport properties of self-doped La 0.... more The effect of hydrostatic pressure P on the magnetic and transport properties of self-doped La 0.94 Mn 0.98 O 3 crystals has been investigated at pressures up to 1 GPa and in the temperature range 15ϽTϽ300 K. It was found that the applied pressure enhances the double-exchange coupling, increases the magnetization, and lowers the ferromagnetic-insulator transition temperature. The results obtained here for the self-doped crystals are compared with those observed for lightly doped La 1Ϫx Sr x MnO 3. It is shown that similar mechanisms of ferromagnetic clustering and percolative polarons may account also for the magnetic and transport properties of the self-doped manganites.

Research paper thumbnail of Effect of pressure and magnetic field on the resistance of the self-doped manganese perovskiteLa0.91Mn0.95O3

Physical Review B

The effect of hydrostatic pressure P up to 9 kbar and applied magnetic fields H up to 15 kOe on t... more The effect of hydrostatic pressure P up to 9 kbar and applied magnetic fields H up to 15 kOe on the transport properties of La 0.91 Mn 0.95 O 3 at temperatures Tϭ77-300 K is reported. At ambient pressure and zero magnetic field the transition to a ferromagnetic phase takes place at T c Ϸ252 K whereas a maximum in resistivity is observed at T r ϭ262 K. It is shown that the maximum in the derivative d(T, P)/dT occurs at the ferromagnetic transition temperature T c. The observed pressure coefficient d ln T c /dPϷ0.0048 kbar Ϫ1 is found to be consistent with Mn ϩ4 concentration of about 40%. The observed behavior of the resistivity (T) at applied magnetic field is analyzed by the mean field theory. It is shown that the maximum of d(T)/dT at applied magnetic field H shifts according to H 2/3 .

Research paper thumbnail of Superconducting properties of GdBa2 - xSrxCu3O7 - delta

Physics of the Solid State

Research paper thumbnail of Magnetism of the Gd3 + sublattice in the system GdBa2 - xSrxCu3O7 - delta

Physics of the Solid State

Research paper thumbnail of Low-temperature structural phase transition of the Jahn-Teller type in DyBa2Cu3O7−δ

Physica C Superconductivity

ABSTRACT

Research paper thumbnail of Pressure effect on transport properties of electron-doped Sm0.2Ca0.8Mn1-xRuxO3(x=0 0.04) manganites

Journal of Applied Physics

ABSTRACT

Research paper thumbnail of Conductivity oscillations in current-induced metastable states in low-doped manganite single crystals

Physical Review B, 2002

Deterministic oscillations of current-induced metastable resistivity in changing voltage have bee... more Deterministic oscillations of current-induced metastable resistivity in changing voltage have been detected in La 0.82 Ca 0.18 MnO 3 single crystals. At low temperatures, below the Curie point, application of specific bias procedures switches the crystal into metastable resistivity state characterized by appearance of pronounced reproducible and random structures in the voltage dependence of the differential conductivity. In certain bias range equally spaced broad conductivity peaks have been observed. The oscillating conductivity has been tentatively ascribed to resonances in a quantum well within the double tunnel barrier of intrinsic weak-links associated with twin-like defect boundaries.

Research paper thumbnail of Current-induced metastable resistive states with memory in low-doped manganites

Physical Review B, 2001

... CAS]. DA Shulyatev, AA Arsenov, SG Karabashev, and Ya.M. Mukovskii, J. Cryst. Growth 198/199,... more ... CAS]. DA Shulyatev, AA Arsenov, SG Karabashev, and Ya.M. Mukovskii, J. Cryst. Growth 198/199, 511 (1999) [INSPEC]. ... 1997 . 14 DA Shulyatev, AA Arsenov, SG Karabashev, and Ya.M. Mukovskii, J. Cryst. Growth 198?99, 511 1999 . ...

Research paper thumbnail of Magnetic ordering of Nd3 + in a NdBa2Cu3O6.3 single crystal

Physics of the Solid State

Research paper thumbnail of Oxygen ordering in the system YBa1.5Sr0.5Cu3Ox under pressure

Physics of the Solid State

ABSTRACT

Research paper thumbnail of Anomalous behavior of the paramagnetic susceptibility of GdBaCuO6.2 single crystals in a magnetic field

Physics of the Solid State

Research paper thumbnail of Superconductivity of the high-Tc system Gd1 + xBa2 - xCu3O7 - delta

Research paper thumbnail of Effect of pressure-induced oxygen ordering on the superconducting properties of GdBa2 - ySryCu3Ox

Physics of the Solid State

Research paper thumbnail of Magnetic transformations in single-crystal GdBaCuO6.2 below 20 K. Determination of the spin interactions of Gd3 + ions

Physics of the Solid State

Research paper thumbnail of Dimensional crossover in the diamagnetic behavior of a GdBaCuO single crystal as the oxygen content is varied

Research paper thumbnail of ChemInform Abstract: Magnetic Properties of Perovskite Manganites and Their Modifications

Research paper thumbnail of Pressure effects on the charge-ordering state in Sm 0.2 Ca 0.8 Mn 1 − x Ru x O 3 ( x = 0 , 0.04 )

Physical Review B, 2001

Transport properties of Sm0.2Ca0.8Mn1-xRuxO3 (x=0,0.04) have been investigated in the temperature... more Transport properties of Sm0.2Ca0.8Mn1-xRuxO3 (x=0,0.04) have been investigated in the temperature range 15-300 K in external magnetic fields up to 1.5 T and hydrostatic pressure up to 1 GPa. The 4% Ru doping in Mn site converts the low-temperature robust orbital ordered phase observed in the undoped compound to a two-phase (ferromagnetic and charge ordered) ground state. As a result of such doping (phase-separated ground state), colossal magnetoresistance, slow relaxation of resistivity with logarithmic time dependence, and prehistory effects that are enhanced by pressure are observed in Sm0.2Ca0.8Mn0.96Ru0.04O3. In contrast, the above effects are absent in Sm0.2Ca0.8MnO3.

Research paper thumbnail of Unconventional exchange bias effect driven by phase separation in basically antiferromagnetic Sm0.1Ca0.6Sr0.3MnO3

Journal of Alloys and Compounds, 2015

ABSTRACT Magnetic investigations, focused on the uncommon behavior of the exchange bias (EB) effe... more ABSTRACT Magnetic investigations, focused on the uncommon behavior of the exchange bias (EB) effect, have been performed for basically antiferromagnetic (AFM) electron doped manganite Sm0.1Ca0.6Sr0.3MnO3. The studied system in the ground state exhibits a heterogeneous spin configuration consisting of the C-type antiferromagnetic phase with the Néel temperature TN�C �≈ 150 K, the G-type AFM phase with the Néel temperature TN�G ≈� 70 K, and a FM-like phase with very weak spontaneous magnetic moment. The phase separation, into two different AFM phases and a FM-like phase at the temperatures below TN–G, leads to nusual magnetic properties, such as: narrowing of magnetic hysteresis loops in field cooling process, unconventional EB effect associated with spontaneous magnetization at temperatures below TN–C, strong magnetic field dependence of the negative exchange bias at fields below 100 Oe turning into practically field independent one for fields above 0.5 kOe, significant shift of EB with temperature with a change of the sign from negative at 10 K to positive above 40 K. The atypical magnetic properties are discussed and related to two different interfaces appearing between coexisting magnetic phases.

Research paper thumbnail of FMR probing of ‘spontaneous’ and Ru-doping induced ferromagnetism in Sm0.2Ca0.8Mn1−xRuxO3 (x≤0.08) manganites

Solid State Communications, 2003

The FMR spectra of electron-doped Sm 0.2 Ca 0.8 Mn 12x Ru x O 3 ð0 # x # 0:08Þ system are measure... more The FMR spectra of electron-doped Sm 0.2 Ca 0.8 Mn 12x Ru x O 3 ð0 # x # 0:08Þ system are measured and analyzed in the temperature interval 100 # T # 320 K; including all critical points of magnetic transitions. It is shown that the origin of macroscopic magnetization in the parent Sm 0.2 Ca 0.8 MnO 3 and Ru-doped compounds is essentially different. The bound magnetic polarons formation at temperatures below the Neel point is suggested to be responsible for the appearance of a minute 'spontaneous' magnetic moment in Sm 0.2 Ca 0.8 MnO 3. Doping with Ru induces formation of 'conventional' ferromagnetic phase in antiferromagnetic matrix. Such a phase is characterized by a Curie temperature, which is higher than the Neel temperature of the matrix. Magnetic phase diagrams of Sm 0.2 Ca 0.8 Mn 12x Ru x O 3 determined by ferromagnetic resonance and dc magnetic measurements are discussed.