The temperature dependence of the heat capacity of the CoFe2O4 ferromagnet and the 0.3CoFe2O4-0.7PbTiO3 multiferroic composite in the temperature range 150-820 K has been studied. heat capacity over a wide temperature range. It is noted that the additional component of the heat capacity is due to the transition of cobalt or iron ions to higher energy levels, as well as due to the distortion of the lattice parameters due to the appearance of three coexisting phases. Keywords: heat capacity, multiferroic composite, Schottky effect.

The temperature dependence of the heat capacity of the CoFe2O4 ferromagnet and the 0.3CoFe2O4–0.7PbTiO3 multiferroic composite in the temperature range 150–820 K has been studied. heat capacity over a wide temperature range. It is noted that the additional component of the heat capacity is due to the transition of cobalt or iron ions to higher energy levels, as well as due to the distortion of the lattice parameters due to the appearance of three coexisting phases.

The temperature dependence of the specific heat of the CoFe2O4 ferromagnet and the 0.3CoFe2O4–0.7PbTiO3 muliferroic composite is studied in the temperature range 150–820 K. An addition of lead titanate ferroelectric to cobalt ferrite ferromagnet is found to lead to a shift of the magnetic phase transition temperature to lower temperatures by 49 K and to a decrease in the specific heat in a wide temperature range. It is noted that the additional component of the specific heat is due to transitions of cobalt or iron ions to higher energy levels and also due to a distortion of the lattice parameters as a result of formation of three coexisting phases.

The temperature dependence of the heat capacity of nanostructured SmFeO3 ceramics obtained by mechanical activation in the temperature range of 120-800 K has been studied. It has been shown that the excess heat capacity of mechanically activated ceramics is due to: displacements of iron and samarium ions and with a change in the angle between FeO6 oxygen octahedra. Keywords: multiferroics, heat capacity, samarium ferrite, Schottky heat capacity, nanostructured ceramics, mechanical activation.

The temperature dependence of the heat capacity of nanostructured SmFeO3 ceramics obtained by mechanical activation in the temperature range of 120–800 K has been studied. It has been shown that the excess heat capacity of mechanically activated ceramics is due to: displacements of iron and samarium ions and with a change in the angle between FeO6 oxygen octahedra.

The temperature dependence of the heat capacity of multiferroics BiFeO3, Bi0.90Sm0.10FeO3, and Bi0.90Eu0.10FeO3 has been investigated. It is found that the substitution of bismuth ions with europium and samarium ions in bismuth ferrite leads to the appearance of an additional heat capacity component due to the transitions of 4f electrons of rare earth ions to higher multiplet levels. A relationship is established between the decrease in phonon thermal conductivity and the Schottky effect for the specific heat.

The temperature dependence of the heat capacity of the multiferroics BiFeO3, Bi0.90Sm0.10FeO3, and Bi0.90Eu0.10FeO3 has been studied. It was found that the substitution of europium and samarium ions for bismuth ions in bismuth ferrite leads to the appearance of an additional heat capacity component due to transitions of 4f - electrons of rare earth ions to higher levels of the multiplet. A connection is established between the decrease in phonon thermal conductivity and the Schottky effect for the specific heat.

The specific heat and the dielectric permittivity of Bi 0.8 Ho 0.2 FeO 3 multiferroics have been studied in the wide temperature range 300–750 K. The doping with rare-earth element holmium is found to lead to substantial changes in the temperature dependences of specific heat C p and dielectric permittivity ε' at high temperatures. The additional contribution to the specific heat is shown can be interpreted as a Schottky anomaly for three-level states which form due to a distortion of the lattice parameters as a result of doping. Additional anomaly characteristic of a phase transition is observed in temperature dependences of C p and ε'. The results are discussed in combination with the data of structural studies.

The heat capacity and permittivity of Bi0.8Ho0.2FeO3 multiferroics were studied in a wide temperature range of 300--750 K. It was found that doping with holmium with rare-earth element leads to significant changes in the temperature dependences of the specific heat Cp and permittivity ε 'at high temperatures. It is shown that an additional contribution to the specific heat can be interpreted as a Schottky anomaly for three-level states arising due to distortion of the lattice parameters upon doping. An additional anomaly characteristic of the phase transition was found in the temperature dependences of Cp and ε '. Research results are discussed in conjunction with structural studies.

The temperature dependence of the thermal diffusivity and thermal conductivity of the multiferroics BiFeO3, Bi0.90Sm0.10FeO3 and Bi0.90Еu0.10FeO3 is studied. It was found that the substitution of bismuth ions by the rare-earth europium and samarium ions in bismuth ferrite leads to a decrease in phonon thermal conductivity in a wide temperature range. It was established that the decrease in the thermal conductivity of bismuth ferrite is due to resonance scattering of phonons at paramagnetic levels of europium and samarium ions.

Temperature dependences of the thermal diffusivity and thermal conductivity in multiferroic materials BiFeO3, Bi0.90Sm0.10FeO3, and Bi0.90Eu0.10FeO3 were studied. Substitution of rare-earth ions of europium and samarium for bismuth ions in bismuth ferrite was found to decrease the phonon thermal conductivity in a wide temperature range. The decrease in the heat conductivity of bismuth ferrite was determined to result from resonance phonon scattering by paramagnetic ions of europium and samarium.

The heat capacity and thermal conductivity of multiferroics Bi1-xPrxFeO3 (0 <= x <= 0.50) has been studied in the temperature range of 130-800 K. A slight substitution of praseodymium for bismuth is found to lead to a noticeable shift of the antiferromagnetic phase transition temperature whilst the heat capacity increases. The temperature dependences of the heat capacity and thermal conductivity exhibit additional anomalies during phase transitions. The experimental results suggest that the excess heat capacity can be attributed to the Schottky effect for three-level states. The basic mechanisms of the heat transfer of phonons are highlighted and the dependence of the mean free path on temperature is determined.

AbstractThe temperature dependence of the specific heat of the Bi_0.95Sm_0.05FeO_3 multiferroic has been studied in the temperature range 130–780 K. The substitution of samarium ions for bismuth ions in the bismuth ferrite is found to lead to the appearance of additional specific heat component that is due to the manifestation of the Schottky effect for three-level states and multiplet structure of 4 f electrons of samarium ions.

The temperature dependence of the specific heat of the Bi 0.95 Sm 0.05 FeO 3 multiferroic has been studied in the temperature range 130–780 K. The substitution of samarium ions for bismuth ions in the bismuth ferrite is found to lead to the appearance of additional specific heat component that is due to the manifestation of the Schottky effect for three-level states and multiplet structure of 4 f electrons of samarium ions.

The impact of mechanical activation on the dielectric properties, structural parameters, and lattice dynamics of the Pb(Zr0.56Ti0.44)O-3 solid solution was investigated. The solution features coexisting metastable tetragonal (T) and rhombohedric (R) phases, whose ratio can be altered by applying the uniaxial compression load up to 320 MPa under torsion in Bridgman anvils. The strain-induced changes of the unit cell parameters, dielectric permittivity, Debye characteristic temperatures, temperature-dependent Debye-Waller factors, and mean square displacements were critically analyzed.

The heat capacity of multiferroics Bi 1– x Pr x FeO 3 (0 ≤ x ≤ 0.20) has been studied in the temperature range 130–800 K. An insignificant substitution of praseodymium for bismuth is found to lead to a noticeable shift of the antiferromagnetic phase transition temperature and to an increase in the heat capacity in the temperature range 240–780 K. The temperature dependence of the excess heat capacity is shown to be due to the Schottky effect for three-level states. The temperature dependences of the heat capacity of the compositions with x = 0.10 and x = 0.15 and 0.20 exhibit additional anomalies characteristic of the phase transitions at T ≈ 755 K and ≈710 K, respectively. The results are discussed in combination with the data of structural studies.

A study of thermal diffusion, heat capacity and thermal conductivity of multiferroic Bi1-xEuxFeO3 (x = 0-0.4) within the range of 130-1200 K is reported. Modifying by admixture of Eu is found to change substantially the thermal anomalies of diffusion and thermal conductivity of the antiferromagnetic phase transition, to increase heat capacity over a wide range of temperatures and to shift the antiferromagnetic transition temperature. The excess heat capacity is shown being related to Schottky effect of three-level states. The mechanisms dominating thermal transfer of phonons at the phase transition and dependence of the mean free path of phonons on the temperature are determined. The results are discussed with account of structural data. (C) 2016 Elsevier B.V. All rights reserved.

Проведены исследования теплоемкости мультиферроиков Bi1-xPrxFeO3 (0≤ x≤ 0.20) в области температур 130-800 K. Обнаружено, что незначительное замещение висмута празеодимом приводит к заметному смещению температуры антиферромагнитного фазового перехода и увеличению теплоемкости в области температур 240-780 K. Показано, что температурная зависимость избыточной теплоемкости обусловлена проявлением эффекта Шоттки для трехуровневых состояний. На температурных зависимостях теплоемкости для составов с x=0.10 и x=0.15, 0.20 обнаружены дополнительные аномалии, характерные для фазовых переходов, при T~ 755 и ~710 K соответственно. Результаты обсуждаются совместно с данными структурных исследований. Работа выполнена при финансовой поддержке госзадания N 16.1103.2014/К, 2560 и РФФИ с использованием оборудования Центра коллективного пользования Института физики ДагНЦ РАН. DOI: 10.21883/FTT.2017.07.44613.434