| Project/Area Number |
17540343
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (C)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
Condensed matter physics II
|
|---|
| Research Institution | National Institute for Materials Science |
|---|
Principal Investigator |
TAICHI Terashima National Institute for Materials Science, Nano System Functionality Center, Senior Reseacher (40343834)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Hiroyuki National Institute for Materials Science, Quantum Beam Center, Senior Reseacher (60354370)
|
|---|
| Project Period (FY) |
2005 – 2007
|
| Project Status |
Completed (Fiscal Year 2007)
|
| Budget Amount *help |
¥3,700,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥300,000)
Fiscal Year 2007: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥1,100,000 (Direct Cost: ¥1,100,000)
|
|---|
| Keywords | strongly-correlated electron systems / magnetism / quantum phase transition / Fermi surface / フェルミ面 |
|---|
| Research Abstract |
We have reported measurements of resistivity in UGe_2 at temperatures down to 0.3 K, pressures up to 19.8 khar, and magnetic fields awl up to 17.5 T applied along the magnetic easy a axis. The coefficient A of the T^2 term of resistivity is determined as a function of Bappl and P. In the large-moment ferromagnetic phase (the low-P/high-Bappl phase), A is found to be a function of the single parameter (Bappl-Bx) and approximately obeys a power law A〜 (Bappl-Bx)_<-1/2>, where Bx is the transition field from the small- to the large-moment ferromagnetic phase. The T dependence of resistivity at fields just above Bx suggests a contribution to the resistivity from excitations with a gapped spectrum.
We have reported an extremely high upper critical field in the noncentrosymmetric heavy fermion superconductor CeRhSi_3 for a magnetic field B along the c axis. Bx_2 (T=0) possibly reaching 30 T is much higher thanBc_2 (0)=7 T fur B normal to c and greatly exceeds the paramagnetic limiting field. The strong anisotropy of Bc_2 (0) with extremely high Bc_2 (0) for B||c is qualitatively explained by the paramagnetic pairbreaking mechanism specific to the noncentrosynunetric superconductor. However an unusual B_2 (T) curve with a positive curvature for B||c cannot be explained satisfactorily by conventional orbital pairbreaking models.
We have reported measurements of the ac magnetic susceptibility and de Haas-van Alphen effect (dHvA) in CeRhSi_3 up to a pressure P=29.5 kbar with the field in the c direction. The observed Fermi surface suggests that Ce 4f electrons are itinerant even when antiferromagnetic order occurs. Effective masses decrease with P: no enhancement is observed as the antiferromagnetic transition temperature is reduced by the application of pressure. Analyses of dHvA oscillations in the mixed state indicate that the influence of the superconducting energy gap is negligible for some orbits.
|
