Awaji Satoshi

High-Field Magnetization Measurements of Fe2MnSi

The high-magnetic-field magnetization measurements of Heusler alloys, Fe2MnSi and Fe2Mn0.8V0.2Si, were performed up to 27 T, and the magnetization \(M\) vs \(T\) measurements were carried out up to 12 T. We observed a magnetic anomaly at 64 K, which persisted even for high magnetic fields at 12 T. We investigated the field dependence of the magnetic anomaly at 64 K on the basis of magnetization measurements and discuss this anomaly with respect to other measurement results. An Arrott plot for \(x = 0\) at 4.2 K indicates that the critical field is approximately 70 T, at which the magnetic moment is 3.0 μB/f.u. It can be inferred that the magnetic transition from the antiferromagnetic state to the ferromagnetic state with a half-metallic band structure occurs, when the magnetization reaches 3.0 μB/f.u. at a critical field of \(B_{\text{s}} = 70\) T.

Fabrication and Properties of Aligned Sr(0.6)K(0.4)Fe(2)As(2) Superconductors by High Magnetic Field Processing

We fabricated a c—axis aligned Sr0.6K0.4Fe2As2 superconductor using a two-step magnetic field procedure. The effect of the magnetic fields on the structure and superconducting properties of Sr0.6K0.4Fe2As2 is investigated using x-ray diffraction and magnetic measurements. The degree of orientation of the samples is about 0.39 for the c axis and 0.51 for ab-plane orientation, as evaluated from the Lotgering factor of x-ray diffraction. This technology may be useful in a variety of potential applications, including preparing iron-based superconducting bulks and wires with high critical currents.

Enhancement of Critical Current Density and Flux Pinning in Acetone and La2O3 Codoped MgB2 Tapes

MgB2 tape samples with simultaneous additions of acetone and La2O3 were prepared by an in-situ processed powder-in-tube method. Compared to the pure and single doped tapes, both transport Jc and fluxing pinning are greatly improved by acetone and La2O3 codoping. Acetone supplies carbon into the MgB2 crystal lattice and increases the upper critical field, while the La2O3 reacts with B to form LaB6 nanoparticles as effective flux pining centers. The improvement of the superconducting properties in codoped tapes can be attributed to the combined effects of improvement in Hc2 and flux pinning.