Takuo Sakon

Magnetotransport properties of (Ga,Mn)As investigated at low temperature and high magnetic field

Abstract Magnetotransport properties of ferromagnetic semiconductor (Ga,Mn)As have been investigated. Measurements at low temperature (50 mK) and high magnetic field ( ⩽27 T ) have been employed in order to determine the hole concentration p=3.5×10 20 cm −3 of a metallic (Ga 0.947 Mn 0.053 )As layer. The analysis of the temperature and magnetic field dependencies of the resistivity in the paramagnetic region was performed using the above value of p , which gave the magnitude of p – d exchange energy |N 0 β|∼1.5 eV .

Magnetic field-induced strain of Ni-Co-Mn-In alloy in pulsed magnetic field

The experimental investigations of a magnetic field-induced strain has been carried out in the Heusler alloy Ni45Co5Mn36.7In13.3 by a capacitance method in a single-shot pulse magnetic field with a frequency of 200 Hz. A 3% deformation has been observed on the application of a maximum pulse field of 70 kOe at 300 K. This indicates an almost complete recovery of the original shape of the alloy. Magnetization shows a clear metamagnetic transition and a large hysteresis at around 300 K, indicating a magnetic field-induced transition from an antiferromagnetic or paramagnetic martensitic state to a ferromagnetic parent phase.

27Al NMR study of the new heavy-fermion superconductors UM2Al3 (M = Ni, Pd)

Abstract We report the nuclear spin-lattice relaxation time T1 and the Knight shift of 27Al of the new heavy-fermion superconductors (HFS), UNi2Al3 and UPd2Al3. The magnetism of these compounds is quite different. In UPd2Al3, the relaxation behavior below Tc is reminiscent of other HFS reported thus far, providing evidence for unconventional superconductivity. The Knight shift has been found to be reduced below Tc, irrespective of the direction of the crystal axes, pointing to the singlet nature of the pairing. In UNi2Al3, however, 1 T 1 and the Knight shift exhibit no indication of anomalies at the superconducting transition.

Superconductivity and magnetism in a single crystal of UPd2Al3

Abstract We present the experimental results of the electrical resistivity under high pressure, magnetic susceptibility and specific heat of single crystalline compounds of nominal composition UPd2Al3 and UPd2Al3.03. From an analysis of the magnetic and superconducting properties, we suggest that the crystalline electric field effect plays an important role in magnetic properties, that the superconducting state has a singlet nature of pairing and that there exist gap zeros on lines on the Fermi surface. Anomalous features in UPd2Al3.03 are also presented.

Magnetic, electrical and thermal properties of heavy fermion superconductor UPd/sub 2/Al/sub 3/

We report experimental results of electrical resistivity, de Haas-van Alphen effect, specific heat and thermal expansion of UPd/sub 2/Al/sub 3/. The nominal composition is denoted by the formula of UPd/sub 2+x/Al/sub 3+y/. Samples with the composition of UPd/sub 2/Al/sub 3.03/ and UPd/sub 2.02/Al/sub 3.03/ reveal de Haas-van Alphen oscillations of the magnetic susceptibility. An anomaly is observed in the superconducting phase in the temperature dependence of the specific heat and thermal expansion of UPd/sub 2/Al/sub 3.03/. The relation between the sample quality and the appearance of the anomaly is discussed. >

Novel Alternating Dimer Chain System (CH3)2NH2CuCl3 Studied by X-ray Structural Analyses and Magnetization Process

The ground-state properties of an S =1/2 quasi-one-dimensional quantum spin system (CH 3 ) 2 NH 2 CuCl 3 were investigated by X-ray structure analyses and high-field magnetization measurements. X-r...

Magnetic properties of bond-alternating quantum spin chain system: (CH3)2NH2CuX3 (X=Cl,Br)

Abstract Magnetic properties of ferromagnetic (F) and antiferromagnetic (AF) bond alternating quantum spin chain system, DMACuX3 where X=Cl, Br and DMA=(CH3)2NH2, are reported. The most prominent result is that for Cl-compound we observed the unusual mixed state in which S=1 and 0 dimers coexist evenly due to frustrated situation in the presence of comparable F and AF couplings. For Br-compound, it is shown from the susceptibility measurements that an AF coupling is dominant and it provides an example of simple dimer-limit.

MAGNETOTUNNELING SPECTROSCOPY OF RESONANT TUNNELING DIODE USING FERROMAGNETIC (GA, MN)AS

Abstract Tunneling and magnetotunneling properties of GaAs-based p-type double barrier resonant tunneling diodes (RTDs) with a ferromagnetic (Ga,Mn)As emitter layer are studied. Current–voltage characteristics of RTDs revealed the presence of spontaneous magnetization in the (Ga,Mn)As emitter. The transverse magnetic field results suggest that the valence band dispersion of (Ga,Mn)As is different from GaAs.

Physical properties of UPd2Al3 at low temperature

Abstract We have measured specific heat, magnetic susceptibility and electrical resistivity of UPd 2 Al 3 and UPd 2 Al 3.03 single crystals. The temperature dependence of the specific heat of UPd 2 Al 3 reveals that the superconducting gap function is anisotropic. We present the results of specific heat measurements of UPd 2 Al 3.03 , suggesting an additional phase transition around 0.6 K.

Is La3Ni a New Unconventional Superconductor

We find that La 3 Ni is a type-II superconductor with a Ginzburg-Landau parameter, κ=49. The temperature dependence of the specific heat reveals two peaks, one of which appears in the superconducting phase and is ascribed to the symmetry change of the superconducting order parameter. We observe nearly T 3 power law dependence of the specific heat, implying that the superconducting energy gap function has nodes on points. The lower critical magnetic field H c1 in the lower temperature phase is larger than that in the higher temperature phase.