| Co-Investigator(Kenkyū-buntansha) |
UYEDA Chiaki Osaka University, Graduate School of Science, Associate professor, 大学院理学研究科, 助教授 (50176591)
FUKUDA Takashi Osaka University, Graduate School of Engineering, Assodate professor, 大学院工学研究科, 講師 (50228912)
TERAI Iomoyuki Osaka University, Graduate School of Engineering, Assistant professor, 大学院工学研究科, 助手 (20346183)
|
|---|
| Research Abstract |
The present study has been motivated to create new functional materials by controlling the crystal structure and microstructure of materials through two kinds of magnetic anisotropy. One is magnetocrystalline anisotropy, which is related to spin. The other is diamagnetic anisotropy, which is not related to spin. Concerning the magnetoaystalline anisotropy, we have investigated the condition for the rearrangement of martensite variants in ferromagnetic shape memory alloys. Concerning the diamagnetic anisotropy, we have measured Ax, of some substances in which the value is not evaluated yet. In addition, we have constructed a new system which evaluates ZSzt in high accuracy.
We examined the rearrangement of martensite variants in some Ni-Mn-Ga alloys with 10M, 14M and 2M structure. In case of the 101V1 martensite, the rearrangement of martensite variants (RMV) by magnetic field occurs at any temperature below its martensitic transformation temperature of 202K In case of the 14M martensite
… More
. RMV by magnetic field occurs only in a limited temperature range of between 309K and 280K In case of the 2M martensite, the RMV by magnetic field does not occur at any temperature. In order to explain these behaviors, we evaluated magnetocrystalline anisotropy and lattice parameter of the martensite phases in a wide temperature range of between 42 K and the transformation temperature. Then, we evaluated the magnetic shear stress acting across the twinning plane, which separates different variants. We also evaluated twinning stress by compressive tests. By comparing the magnetic shear stress and twinning stress, it became obvious that the condition for the RMV by magnetic field can be expressed as the following: the magnetic shear stress is larger than the twinning stress.
In evaluating Ax of diamagnetic substances, we have achieved a high precision of 1×10^<-9> emu/g by using a microgravity technique. We have checked the accuracy of the method by comparing Δx of quarts and corundum crystals obtained by the present method with those of previous studies. We also created an instrument which can examine alignment of diamagnetic particles in He gas (dispersing medium) in a temperature range between ambient temperature down to 40 K. Using the instrument, we have examined the alignment of graphite particles, and found that the magnetic field required for the alignment is proportional to T^<1/2>, being in good agreement with theory for the alignment. Less
|
