Magnetic phase transitions in solid solutions of Fe-containing perovskite multiferoics

This study was supported by RFBR (project 18-52-00029_a) and by the Ministry of Education and Science of the Russian Federation (project 3.1649.2017/4.6)

Tuning relaxor and magnetic properties of complex perovskites by varying the compositional ordering degree

This work was supported in part by RFBR (projects 17-03-01293_a and 18-52-00029 Bel_a), Belarussian Republican Foundation for Fundamental Researches (grant T18R-048) and by the Ministry of Education and Science of the Russian Federation (research project 3.1649.2017/4.6)

Upconversion Luminescence of Er3+ Ions from Barium Titanate Xerogel Powder and Target Fabricated by Explosive Compaction Method

Photo- and cathodoluminescence in the visible range from erbium-doped barium titanate xerogels obtained in the form of a powder and a target pressed from it by explosive compaction are investigated. The powder and target exhibit upconversion luminescence of erbium ions excited at wavelengths in the regions 950–1000 and 1450–1550 nm that is characterized by strong bands at 650 and 520–560 nm and a weak band at ~820 nm that correspond to the 4F9/2 → 4I15/2, 2H11/2 → 4I15/2, 4S3/2 → 4I15/2, and 4I9/2 → 4I15/2 transitions of Er3+. The target also demonstrates cathodoluminescence at room temperature and liquid nitrogen temperature with the strongest bands at 650, 520, and 538 nm

Тhe effect of Cr substitution for Fe on ferroelectric and magnetic properties of PbFe0.5Nb0.5O3, PbFe0.5Sb0.5O3 and BiFeO3 multiferroics

Проведены диэлектрические и мессбауэровские исследования сегнетоэлектрических и магнитных фазовых переходов в твердых растворах PbFe0.5-xCrxNb0.5O3, BiFe1-xCrxO3, PbFe0.5-xCrxSb0.5O3. Во всех этих системах замещение железа хромом разрушает как сегнетоэлектрический, так и магнитный дальний порядок.PbFe0.5-xCrxNb0.5O3, BiFe1-xCrxO3, PbFe0.5-xCrxSb0.5O3 solid solutions have been carried out. In all the systems studied Cr substitution for Fe destroys both ferroelectric and magnetic long-range order.Работа выполнена при поддержке Российского Фонда Фундаментальных Исследований (грант 16-52-0072 Бел_a) и Белорусского Республиканского Фонда Фундаментальных Исследований (грант T16R-079)

Dielectric and Mossbauer studies of ASnO3 - and AFe1/2B1/2O3 - based ceramics (A-Ba, Cd; B- Nb, Sb) exhibiting giant dielectric response

Установлено, что гигантские значения диэлектрической проницаемости керамик на основе ASnO3 и AFe1/2B1/2O3 (A-Ba, Cd; B- Nb, Sb) обусловлены релаксационной поляризацией Максвелл-Вагнеровского типа. Из исследований мессбауэровских спектров получена информация о валентности Sn и Fe в данных материалах.Giant dielectric permittivity of ASnO3 - and AFe1/2B1/2O3 - based ceramics (A-Ba, Cd; B-Nb, Sb) was shown to be due to Maxwell-Wagner relaxation. Information on the valence of Sn and Fe ions was o tained from Мöss auer studies.Работа выполнена при поддержке Проектной части Госзадания Минобрнауки № 3.1649.2017/ПЧ

Structural and magnetic phase transitions in the Fe-rich compositional range of the multiferroic BiFe1-x[Zn0.5Ti0.5]xO3 perovskites

The (1-x)BiFeO3-xBiZn0.5Ti0.5O3 solid solutions (0.05 ≤ x ≤ 0.25) were prepared using high-pressure synthesis. Up to 25 at.% substitutions of Fe by the combination of [Mg0.5Ti0.5] were found to increase the unit cell volume of the primitive perovskite cell, while the crystal structure remains the rhombohedral perovskite, as that in the parent BiFeO3. With increasing temperature, the as-prepared ceramics of the x ¼ 0.25 composition reversibly transform into a cubic modification between about 970 and 1070 K. However, this phase transition is overlapped with a gradual decomposition of the perovskite phase, which starts above 770 K. The perovskite phase with the substitution rate corresponding to x ¼ 0.25 is antiferromagnetic below TN460 K. Peculiarities of the temperature-dependent magnetic behavior of this composition at about 220 and 315 K, which might indicate transitions between the states with different magnetic orderings, have been observed.publishe

Structural Dependent Eu3+ Luminescence, Photoelectric and Hysteresis Effects in Porous Strontium Titanate

Eu3+ doped porous nanostructured SrTiO3 films and powder fabricated by sol-gel route without using any precursor template are characterized by different morphology and phase composition. The films and the power show red and yellow luminescence with the most intensive photoluminescence (PL) bands at 612 nm and 588 nm, respectively. Raman, secondary ion mass spectrometry(SIMS), andX-ray diffraction(XRD) analysisof undopednanostructuredporousSrTiO3 films showed the presence of TiO2, SrO, and SrTiO3 phases and their components. The undoped porous SrTiO3 films are photosensitive and demonstrate resistive switching. The capacitance-voltage hysteresis loops with the width of about 6 V in the frequency range of 2 kHz—2 MHz were observed