Магнитные свойства высококоэрцитивных ферритов Sr1-xGdxFe12-xCoxO19 (0 ≤ x ≤ 0,5)

Sr1-xGdxFe12-xCoxO19 ( x = 0; 0.1; 0.2; 0.3; 0.4; 0.5) ferrites have been prepared by solid-state method under air at 1473 K. It has been found that increasing the value of x first leads to a slight decrease in the Curie temperature, from 727 K for the base ferrite SrFe12O19 to 725 K of solid solution Sr0.9Gd0.1Fe11.9Co0.1O19, but with x further increasing, the Curie temperature rises reaching 745 K at x=0.5. It has been found that at 5 K and 300 K, spontaneous magnetization (no) values are respectively 4.2 and 3.7 % higher for solid solution Sr0.9Gd0.1Fe11.9Co0.1O19 than for the base ferrite SrFe12O19.Твердофазным методом на воздухе при температуре 1473 K получены образцы ферритов Sr1-xGdxFe12-xCoxO19 ( x = 0; 0,1; 0,2; 0,3; 0,4; 0,5). Рентгенофазовый анализ показал, что образцы с x≥0,2, кроме основной фазы со структурой магнетоплюмбита, содержали примесные фазы α-Fe2O3, Gd3Fe5O12, в образцах с x=0,3; 0,4; 0,5 присутствовали фазы GdFeO3, CoFe2O4, а в образцах с x=0,4; 0,5 - фаза Gd2O3. Установлено, что увеличение параметра состава x сначала приводит к незначительному уменьшению температуры Кюри от 727 K для SrFe12O19 до 725 K для феррита с x=0,1, а при дальнейшем увеличении x до 0,5 она немного возрастает и для образцов с x=0,5 составляет 745 K. Установлено, что твердый раствор феррита Sr1-xGdxFe12-xCoxO19 с x=0,1 при 5 и 300 K имеет значения самопроизвольной намагниченности (и0) больше, чем у феррита SrFe12O19 на 4,2 и 3,7 % соответственно

Crystal structure, magnetic and electrical properties and thermal expansion of ferrites of the system Sr1–xSmxFe12–xZnxO19 ( x= 0–0.5)

High-coercivity ferrite samples Sr1–xSmxFe12–xZnxO19 (x = 0–0.5) with magnetoplumbite structure were prepared from oxides Fe2O3, Sm2O3, ZnO and carbonate SrCO3by solid-state ceramic method, the dependence of the unit cell parameters aand con the value of x was determined. It was determined that samples of Sr1–xSmxFe12–xZnxO19were single-phased up to x= 0.2, and also contained ?-Fe2O3for x ?0.3 phase, quantity of which gradually increased with increasing xup to 0.5, and small quantities of phases ZnFe2O4and SmFeO3were present in the samples with x= 0.4 and 0.5. The magnetic, electrical properties and thermal expansion of these ferrite samples were studied, the values of specific saturation magnetization (?s ) were determined by magnetic hysteresis loops at 5 and 300 K. It was found that the solid solution Sr0.9Sm0.1Fe11.9Zn0.1O19at 300 K has specific saturation magnetization (?s ) and coercive force (?Hc) respectively by 0.4 and 9.7% higher than the base ferrite SrFe12O19

Crystal structure and magnetic properties of Gd1-xLaxMO3 (M= Sc, In, Ga) solid solutions

Gd1–xLaxScO3, Gd1–xLaxInO3and Gd1–xLaxGaO3solid solutions were synthesized by the ceramic method, their crystal structure and magnetic properties were investigated. It has been established that the range of solid solutions Gd1–xLaxScO3(0.0 < х ?1.0), Gd1–xLaxInO3(0.2 ? х ?1.0) and Gd1–xLaxGaO3(0.5 ? х ?1.0) with the structure of orthorhombically distorted perovskite was formed. The effective magnetic moment of the Gd 3+ ion (µef, Gd 3+) for Gd1–xLaxScO3solid solutions with x= 0.10, 0.50 is equal to 7.76 ?В, 7.61 µВ, respectively and it is slightly lower than the theoretical value ?ef. theor, Gd 3+= 7.94 µВ, and for x= 0.75, 0.90 it is practically equal to the theoretical value. For Gd1–xLaxGaO3solid solutions with x= 0.8, 0.9 the effective magnetic moment ?ef, Gd 3+ is 7.90 ?В, 7.99 ?В, respectively, and it is close to the theoretical value 7.94 ?В. For Gd1–xLaxInO3solid solutions the effective magnetic moment ?ef, Gd 3+ varies without certain dependence in the interval from 6.91 ?Вto 7.54 µВand is lower than theoretical value ?эф. теор, Gd 3+

Magnetic properties of solid solutions of BiFeO3– SmCoO3 system

Solid solutions of BiFeO3– SmCoO3were synthesized by a solid-state method. Peculiarities of the influence of isovalent substitution of Bi 3+ and Fe 3+ ions in BiFeO3by Sm 3+ , Co 3+ ions on the crystal structure and magnetic properties of Bi1–xSmxFe1–xCoxO3solid solutions are found. It is shown that the substitution 3-25% of the Bi 3+ , Fe 3+ ions in BiFe0O3by Sm 3+ , Co 3+ ions results in the gradual destruction of the antiferromagnetic and conception of ferromagnetic ordering. In this case replacing up to 10% of Sm 3+ and Co 3+ ions in SmCoO3by Bi 3+ and Fe 3+ ions leads to the stabilization of Co 3+ ions in a diamagnetic state

Influence of oxygen vacancies on the magnetic and electrical properties of La 1−x\mathsf{_{1-x}} Sr x\mathsf{_{x}} MnO 3−x/2\mathsf{_{3-x/2}} manganites

The crystal structure, magnetization and electrical transport depending on the temperature and magnetic field for the doped stoichiometric ${\rm La}_{1-x}^{3 + } {\rm Sr}_x^{2 + } {\rm Mn}_{1-x}^{3 + } {\rm Mn}_x^{4 + } {\rm O}_3^{2-}$ as well as anion-deficient ${\rm La}_{1-x}^{3 + } {\rm Sr}_x^{2 + } {\rm Mn}^{3 + }{\rm O}_{3-x/2}^{2-}$ ( $0\le x \le 0.30$ ) ortomanganite systems have been experimentally studied. It is established that the stochiometric samples in the region of the $0 \le x \le 0.125$ are an ${\rm O}'$ -orthorhombic perovskites whereas in the $0.175 \le x \le 0.30$ - a rhombohedric. For the anion-deficient system the symmetry type of the unit cell is similar to the stoichiometric one. As a doping level increases the samples in the ground state undergo a number of the magnetic transitions. It is assumed that the samples with the large amount of oxygen vacancies are a cluster spin glasses ( $0.175 > x \le 0.30$ ) and temperature of the magnetic moment freezing is ~40 K. All the anion-deficient samples are semiconductors and show considerable magnetoresistance over a wide temperature range with a peak for the x=0.175 only. Concentration dependences of the spontaneous magnetization and magnetic ordering temperature for the anion-deficient ${\rm La}_{1-x}^{3 + } {\rm Sr}_x^{2 + } {\rm Mn}^{3 + }{\rm O}_{3-x/2}^{2-}$ system have been established by the magnetic measurements and compared with those for the stoichiometric ${\rm La}_{1-x}^{3 + } {\rm Sr}_x^{2 + } {\rm Mn}_{1-x}^{3 + } {\rm Mn}_x^{4 + } {\rm O}_3^{2-}$ one. The magnetic propeprties of the anion-deficient samples may be interpreted on the base of the superexchange interaction and phase separation (chemical disorder) models. Copyright Springer-Verlag Berlin/Heidelberg 2004