Pressure effect on magnetic susceptibility and exchange interactions in GdMx (x = 1, 2, 3, 5) systems

Effect of pressure on electronic structure and magnetic properties of GdMx (x = 1, 2, 3, 5) systems is studied experimentally and theoretically. By employing the ab initio electronic structure calculations, the magnetic susceptibilities, saturation moments, exchange parameters, magnetic ordering temperature and their pressure derivatives are evaluated and appeared to be consistent with available experimental data. The obtained results are expected to promote further advance in the theory of magnetic ordering in rare-earth systems

Anisotropic magnetoresistive and magnetic properties of La₀.₅Sr₀.₅CoO₃₋δ film

The magnetic and transport properties of a La₀.₅Sr₀.₅CoO₃₋δ film grown on a LaAlO₃ substrate by pulsed-laser deposition are studied. The properties are found to be influenced by the magnetic anisotropy and inhomogeneity. Magnetoresistance anisotropy is determined by the shape anisotropy of the magnetization and the strain-induced magnetic anisotropy due to the film-substrate lattice interaction. Indications of the temperature-driven spin reorientation transition from an out-of plane orderded state at low temperatures to an in-plane ordered state at high temperatures as a result of competition between the mentioned sources of magnetic anisotropy are found

Pressure effect on magnetic properties of gadolinium in paramagnetic state

In this report we are mostly focused on refinement of the experimental dependence of the magnetic transition temperature TC on pressure under pure hydrostatic (gaseous) conditions. Unlike previously used methods, we employed a new procedure, based on the measurement of pressure effect on the dc magnetic susceptibility of Gd in the paramagnetic state at temperatures above TC. The dc paramagnetic susceptibility of Gd was measured in the temperature range of 295−365 K and under hydrostatic pressure up to 0.16 GPa, yielding values of the paramagnetic Curie temperature Θ and its pressure derivative. Also we explored a possibility to describe pressure effects on magnetism of Gd within simple mean-field approaches, which are based on ab initio electronic structure calculations. Based on the results of electronic structure calculations within the density functional theory, the experimental behavior of Θ under pressure was described in the framework of mean-field like approach.Проведены измерения парамагнитной восприимчивости Gd в интервале температур 295−365 K в условиях гидростатического сжатия до 0.16 GPa, что позволило получить значения парамагнитной температуры Кюри Θ и ее производной по давлению. Основываясь на результатах расчетов электронной структуры с использованием теории функционала плотности, было исследовано поведение Θ под давлением в рамках теории среднего поля. С этой целью были вычислены эффективная восприимчивость зонных d-электронов и соответствующие обменные интегралы как функции параметров решетки.Було виміряно парамагнітну сприйнятливість Gd в інтервалі температур 295−365 K в умовах гідростатичного тиску до 0.16 GPa, що дозволило отримати значення парамагнітної температури Кюрі Θ та її похідної за тиском. На основі результатів розрахунків електронної структури з використанням теорії функціонала густини було досліджено поведінку Θ під тиском у рамках теорії середнього поля. З цією метою були обчислені ефективна сприйнятливість зонних d-станів і відповідні обмінні інтеграли як функції параметрів ґратки

Magnetoresistance and magnetic anisotropy in La0.5_{0.5}Sr0.5_{0.5}CoO3−δ_{3-\delta} film

The magnetic and transport properties of La$_{0.5}$Sr$_{0.5}$CoO$_{3-\delta}$ film grown on a LaAlO$_3$ substrate by pulsed-laser deposition are studied. The properties are found to be influenced by a combined influence of the magnetic anisotropy and inhomogeneity. Magnetoresistance anisotropy is determined by the shape anisotropy and the strain-induced magnetic anisotropy due to the film-substrate lattice interaction. Indications of the temperature-driven spin reorientation transition from an out-of plane orderded state at low temperatures to an in-plane ordered state at high temperatures as a result of competition between the mentioned anisotropy sources are found.Comment: 3 pages, 4 figures, reported at Moscow Int. Symp. on Magnetism (MISM 2002), June 200

Giant magnetic-field changes in radio-frequency absorption in La0.67_{0.67}Sr0.33_{0.33}MnO3_3 near the Curie temperature

The DC transport properties of and the radio-frequency (RF) wave absorption (at 2.525 MHz) in a sample of La$_{0.67}$Sr$_{0.33}$MnO$_{3}$ prepared by floating-zone method are measured. The Curie temperature, $T_{c}$, of the sample is about 374 K. Giant temperature and magnetic-field variations in RF absorption are found in the vicinity of $T_{c}$. Relative change of the RF absorption in magnetic field (magnetoabsorption) is about 67% in field 2.1 kOe and about 55% in field 1 kOe. This giant magnetoabsorption effect can be used to develop RF devices controlled by temperature and low magnetic field. A weak temperature dependence of magnetoabsorption for the sample studied in the range from room temperature to about 350 K makes it especially attractive for practical use. The RF study supplemented with transport, magnetoresistive and magnetic measurements enables us to discuss the optimal properties of manganite samples for observation of giant magnetoabsorption in low field.Comment: Submitted to J. Magn. Magn. Mater., 14 pages including 7 figure

Paradoxical Onset of Arrhythmic Waves from Depolarized Areas in Cardiac Tissue Due to Curvature-Dependent Instability 0

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Effect of pressure on the magnetic properties of CrB₂

Magnetic susceptibility c of the itinerant antiferromagnet CrB₂ with TN ≃ 87K was studied as a function of the hydrostatic pressure up to 2 kbar at fixed temperatures 78 and 300 K. The pressure effect on c is found to be negative in sign and weakly dependent on the magnetic state of the compound. In addition, the measured pressure dependence of the Néel temperature, dTN / dP = (0.1 ± 0.1) K/kbar, is roughly two orders of magnitude smaller than the corresponding value for the pure chromium. The main contributions to c and their volume dependence are calculated ab initio within the local spin density approximation, and appeared to be in close agreement with the experimental data

Magnetovolume effect in Ce(Ni1−xCux)₅ alloys

Magnetic susceptibility χ of the isostructural Ce(Ni1−xCux)₅ alloys (0 ≤ x ≤ 0.9) was studied as a function of the hydrostatic pressure up to 2 kbar at fixed temperatures of 77.3 and 300 K, using a pendulum-type magnetometer. A pronounced pressure effect on χ is found to be negative in sign and strongly (non-monotonously) dependent on the Cu content, showing a sharp maximum at x ≅ 0.4. The experimental results are discussed in terms of the valence instability of Ce ion in the studied alloys. For the reference CeNi₅ compound the main contributions to χ and their volume dependence are calculated ab initio within the local spin density approximation (LSDA), and appeared to be in close agreement with experimental data

Magnetoresistive study of the antiferromagnetic-weak ferromagnetic transition in single-crystal La₂CuO₄+δ

Resistive measurements were made to study the magnetic field-induced antiferromagnetic (AF)—weak ferromagnetic (WF) transition in the La₂CuO₄ single crystal. The magnetic field (dc or pulsed) was applied normally to the CuO₂ layers. The transition manifested itself in a drastic decrease of the resistance in critical fields of 5–7 T. The study is the first to display the effect of the AF–WF transition on the conductivity of the La₂CuO₄ single crystal in the direction parallel to the CuO₂ layers. The results provide support for the three-dimensional nature of the hopping conduction of this layered oxide

Pressure effect on magnetic properties of valence fluctuating system Ce(Ni₁₋xCux)₅

Magnetic susceptibility χ of the isostructural Ce(Ni₁₋xCux)₅ alloys (0 ≤ x ≤ 0.9) was studied as a function of the hydrostatic pressure up to 2 kbar at fixed temperatures 77.3 and 300 K. A pronounced pressure effect on susceptibility is found to be negative in sign and nonmonotonously dependent on the Cu content, showing a sharp maximum at x 0.4. The experimental results are discussed in terms of the valence instability of Ce ion in the studied alloys. For the reference CeNi5 compound the main contributions to χ and their volume dependence are calculated ab initio within the local spin density approximation, and appeared to be in close agreement with experimental data