Search

LaCrGe3 is an itinerant ferromagnet with a Curie temperature of TC=85 K and exhibits an avoided ferromagnetic quantum critical point under pressure through a modulated antiferromagnetic phase as well as tricritical wing structure in its temperature-pressure-magnetic field (T-p-H) phase diagram. In order to understand the static and dynamical magnetic properties of LaCrGe3, we carried out La139 nuclear magnetic resonance (NMR) measurements. Based on the analysis of NMR data, using the self-consistent-renormalization (SCR) theory, the spin fluctuations in the paramagnetic state are revealed to be isotropic ferromagnetic and three dimensional (3D) in nature. Moreover, the system is found to follow the generalized Rhodes-Wohlfarth relation which is expected in 3D itinerant ferromagnetic systems. As compared to other similar itinerant ferromagnets, the Cr 3d electrons and their spin fluctuations are characterized to have a relatively high degree of localization in real space.

LaCrGe3 is an itinerant ferromagnet with a Curie temperature of TC=85 K and exhibits an avoided ferromagnetic quantum critical point under pressure through a modulated antiferromagnetic phase as well as tricritical wing structure in its temperature-pressure-magnetic field (T-p-H) phase diagram. In order to understand the static and dynamical magnetic properties of LaCrGe3, we carried out La139 nuclear magnetic resonance (NMR) measurements. Based on the analysis of NMR data, using the self-consistent-renormalization (SCR) theory, the spin fluctuations in the paramagnetic state are revealed to be isotropic ferromagnetic and three dimensional (3D) in nature. Moreover, the system is found to follow the generalized Rhodes-Wohlfarth relation which is expected in 3D itinerant ferromagnetic systems. As compared to other similar itinerant ferromagnets, the Cr 3d electrons and their spin fluctuations are characterized to have a relatively high degree of localization in real space.

In conventional metals, modification of electron trajectories under magnetic field gives rise to a magnetoresistance that varies quadratically at low field, followed by a saturation at high field for closed orbits on the Fermi surface. Deviations from the conventional behaviour, for example, the observation of a linear magnetoresistance, or a non-saturating magnetoresistance, have been attributed to exotic electron scattering mechanisms. Recently, linear magnetoresistance has been observed in many Dirac materials, in which the electron–electron correlation is relatively weak. The strongly correlated helimagnet CrAs undergoes a quantum phase transition to a nonmagnetic superconductor under pressure. Here we observe, near the magnetic instability, a large and non-saturating quasilinear magnetoresistance from the upper critical field to 14 T at low temperatures. We show that the quasilinear magnetoresistance may arise from an intricate interplay between a nontrivial band crossing protected by nonsymmorphic crystal symmetry and strong magnetic fluctuations.

We have performed NMR measurements under pressure in UCoAl with a quantum critical endpoint of the metamagnetic transition from the paramagnetic phase to the ferromagnetic (FM) phase. 59 Co-NMR sensitively detects the evolution of the internal field caused by applying the external field. The metamagnetic field H m increases with increasing pressure consistently with other experimental methods, accompanied by the suppression of the magnetization in the field-induced FM phase and the magnetization jump at H m . The loss of the NMR signal on approaching the QCEP indicates the development of the spin fluctuations. © 2013 The Korean Physical Society.

We have performed NMR measurements under pressure in UCoAl with a quantum critical endpoint of the metamagnetic transition from the paramagnetic phase to the ferromagnetic (FM) phase. 59 Co-NMR sensitively detects the evolution of the internal field caused by applying the external field. The metamagnetic field H m increases with increasing pressure consistently with other experimental methods, accompanied by the suppression of the magnetization in the field-induced FM phase and the magnetization jump at H m . The loss of the NMR signal on approaching the QCEP indicates the development of the spin fluctuations. © 2013 The Korean Physical Society.

We report 59Co-NMR measurements in UCoAl where metamagnetism occurs owing to the enhancement of ferromagnetism by a magnetic field. The metamagnetic transition from a paramagnetic (PM) state to a ferromagnetic state is a first-order transition at low temperatures, but it changes to a crossover at high temperatures on crossing the critical end point (CEP) at Tcep ∼ 12 K. The contrasting behavior between the relaxation rates 1/T 1 and 1/T2 suggests that the longitudinal magnetic fluctuation of the U moments is strongly enhanced, especially near the CEP. A wide diffusion of the fluctuation from the CEP can be confirmed even in the PM state where the magnetic transition does not occur. © 2011 The Physical Society of Japan.

We report 59Co-NMR measurements in UCoAl where metamagnetism occurs owing to the enhancement of ferromagnetism by a magnetic field. The metamagnetic transition from a paramagnetic (PM) state to a ferromagnetic state is a first-order transition at low temperatures, but it changes to a crossover at high temperatures on crossing the critical end point (CEP) at Tcep ∼ 12 K. The contrasting behavior between the relaxation rates 1/T 1 and 1/T2 suggests that the longitudinal magnetic fluctuation of the U moments is strongly enhanced, especially near the CEP. A wide diffusion of the fluctuation from the CEP can be confirmed even in the PM state where the magnetic transition does not occur. © 2011 The Physical Society of Japan.

Thermal expansion coefficient in single-walled carbon nanotube bundles was determined as (－0.15±0.20)×10^<－5> (1/K) for the tube diameter and (0.75±0.25)×10^<－5> (1/K) for the triangular lattice constant by means of x-ray scattering between 300 K to 950 K. The value for the intertube gap was (4.2±1.4) ×10^<－5> (1/K), which is larger than 2.6×10^<－5> (1/K) for the c-axis thermal expansion in graphite. The results reveal the presence of a remarkably larger lattice anharmonicity in nanotube bundles than that of graphite. The small value for the tube diameter is consistent with the seamless tube structure formed by a strong covalent bond between carbon atoms comparable to that in graphite., identifier:10980121, identifier:https://dspace.jaist.ac.jp/dspace/handle/10119/3359

Thermal expansion coefficient in single-walled carbon nanotube bundles was determined as (－0.15±0.20)×10^<－5> (1/K) for the tube diameter and (0.75±0.25)×10^<－5> (1/K) for the triangular lattice constant by means of x-ray scattering between 300 K to 950 K. The value for the intertube gap was (4.2±1.4) ×10^<－5> (1/K), which is larger than 2.6×10^<－5> (1/K) for the c-axis thermal expansion in graphite. The results reveal the presence of a remarkably larger lattice anharmonicity in nanotube bundles than that of graphite. The small value for the tube diameter is consistent with the seamless tube structure formed by a strong covalent bond between carbon atoms comparable to that in graphite.