We report muon spin rotation and magnetic susceptibility experiments on in-plane stress effects on the static spin-stripe order and superconductivity in the cuprate system La 2−x Ba x CuO 4 with x ¼ 0.115. An extremely low uniaxial stress of ∼0.1 GPa induces a substantial decrease in the magnetic volume fraction and a dramatic rise in the onset of 3D superconductivity, from ∼10 to 32 K; however, the onset of at-least-2D superconductivity is much less sensitive to stress. These results show not only that largevolume-fraction spin-stripe order is anticorrelated with 3D superconducting coherence but also that these states are energetically very finely balanced. Moreover, the onset temperatures of 3D superconductivity and spin-stripe order are very similar in the large stress regime. These results strongly suggest a similar pairing mechanism for spin-stripe order and the spatially modulated 2D and uniform 3D superconducting orders, imposing an important constraint on theoretical models.

No abstract

The maximum energy products, (BH)max, of isotropic Nd-Fe-B-based nanocomposite magnets were calculated by a three dimensional model (10×10×10) that incorporated non-uniform magnetization reversals by subdivisions of the grains. Based on the results of our simulation, the largest obtainable (BH)max for a sample with 60% soft and 40% hard grains is about 290 kJ/m3. This value is lower than the previous crude estimate of 400 kJ/m3 but is almost twice as large as the experimental measured maximum of 160 kJ/m3 suggesting that further improvement in (BH)max is possible if the nanostructure of an actual magnet can made close to the theoretically ideal structure.