Papers by Keyword: Paramagnetic Susceptibility

Abstract: Thermopower α and magnetothermopower ∆α/α were studied in the Sm_0.55Sr_0.45MnO₃ samples, containing clusters of three types: ferromagnetic clusters with the Curie temperature T_C = 126 K, A-type antiferromagnetic clusters with the Neel temperature T_NA ≥ T_C and CE-type antiferromagnetic clusters with the T_NCE = 240 K. The curves of temperature dependence of α (T) have a large maximum including T_C and T_NCE and the sharp minimum on the {∆α/α}(T) curves in the T_C-region. Negative magnetothermopower in minimum achieves the giant value ~ 85% in magnetic field 14.17 kOe. It is shown that thermopower is largely caused by the presence of ferromagnetic nanoclusters of ferron-type and to a lesser degree of CE-type antiferromagnetic clusters, in which there is a charge ordering, displacing oxygen ions.

Abstract: Thermopower α and magnetothermopower α/α were studied in the single-crystal Sm_0.55Sr_0.45MnO₃ samples, containing clusters of three types: ferromagnetic clusters with the Curie temperature T_C = 134 K, A-type antiferromagnetic clusters with the Neel temperature T_NA T_C and CE-type antiferromagnetic clusters with the T_NCE = 240 K. The curves of temperature dependence of α (T) and {α/α}(T) have extrema in the T_NCE-region: large maximum on the first and sharp minimum on the second. Negative magnetothermopower in minimum achieves the giant value 50% in magnetic field 13,2 kOe. It is shown that thermopower is essentially caused by the presence of CE-type antiferromagnetic clusters, in which exists charge order, displacing oxygen ions

Abstract: Magnetocaloric effect (T-effect) was studied by direct method on three samples of Sm0.55Sr0.45MnO3 manganite: ceramic (C) sample and two single crystals, annealed in oxygen (O) or in air atmosphere (A). The temperature dependence of T-effect T(T) of all the samples has maximum at Tmax equal to 143.3 K for A-sample, 244 K for O-sample, and 143 K for C-sample. In these maxima T values are 0.8 K, 0.41 K, and 0.4 K for A-, O- and C-samples respectively. In addition, the T(T) curve of A-sample has minimum at Tmin = 120 K and T-value in minimum is equal to - 0.1 K. The maximum value of T-effect increases with H up to the maximum field of measurement 14.2 kOe. When this takes place the rate of this increasing is higher at H > 8 kOe than at H < 8 kOe. The above listed peculiarities of T-effect are explained by the presence in the samples of ferromagnetic, antiferromagnetic A-type and antiferromagnetic CE-type clusters.

Abstract: Magnetic properties of Ni3Al1-yMny alloys at y≤0.6 were investigated at T≤400 K in magnetic fields H≤4 MA/m. The concentration y dependencies of the spontaneous magnetic moment s, the effective magnetic moment eff, the Curie temperature ТС, the Weiss constant , and the temperature independent part of the magnetic susceptibility 0 were determined. The behavior of the Rhodes-Wohlfarth parameter р(y) in the transition region from the itinerant electron magnetism to the spin localized one is related to the increase in the spontaneous magnetic moment of Ni atoms inversely proportional to the average distance between Mn atoms with the highly localized magnetic moments.