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N. Onishi

Publications and source records attributed to N. Onishi.

7 recordsLinked to original sources
arXiv2011

Magnetic Frustration in a Mn Honeycomb Lattice Induced by Mn-O-O-Mn Pathways

We investigated the electronic structure of layered Mn oxide Bi3Mn4O12(NO3) with a Mn honeycomb lattice by x-ray absorption spectroscopy. The valence of Mn was determined to be 4+ with a small charge-transfer energy. We estimated the values of superexchange interactions up to the fourth nearest neighbors (J1, J2, J3, and J4) by unrestricted Hartree-Fock calculations and a perturbation method. We found that the absolute values of J1 through J4 are similar with positive (antiferromagnetic) J1 and J4, and negative (ferromagnetic) J2 and J3, due to Mn-O-O-Mn pathways activated by the smallness of charge-transfer energy. The negative J3 provides magnetic frustration in the honeycomb lattice to prevent long-range ordering.

cond-mat.str-el↗
arXiv2007

Moment distributiuons of clusters and molecules in the adiabatic rotor model

We present a Fortran program to compute the distribution of dipole moments of free particles for use in analyzing molecular beams experiments that measure moments by deflection in an inhomogeneous field. The theory is the same for magnetic and electric dipole moments, and is based on a thermal ensemble of classical particles that are free to rotate and that have moment vectors aligned along a principal axis of rotation. The theory has two parameters, the ratio of the magnetic (or electric) dipole energy to the thermal energy, and the ratio of moments of inertia of the rotor.

physics.comp-ph↗
arXiv2001

Wobbling Motion in the multi-bands crossing region: dynamical coupling mode between high- and low-K states

We analyze a mechanism of coupling of high- and low-$K$ bands in terms of a dynamical treatment for nuclear rotations, i.e.,wobbling motion. The wobbling states are produced through the generator coordinate method after angular momentum projection ({\it GCM-after-AMP}), in which the intrinsic states are constructed through fully self-consistent calculations by the 2d-cranked (or tilted-axis-cranked) HFB method . In particular, the phenomena of ``signature inversion'' and ``signature splitting'' in the t-band (tilted rotational band) are explained in terms of the wobbling model. % Our calculations will be compared with new data for in-band E2 transition rates in $^{182}$Os, which may shed light on the mechanism of the anomalous K=25 isomer decay, directly to the yrast band.

nucl-th↗
arXiv1998

Coupling between electron-spin and ferromagnetic clusters

We analyze the adiabatic magnetization of ferromagnetic clusters in an intermediate coupling regime, where the anisotropic potential is comparable to other energy scales. We find a non-monotonic behavior of the magnetic susceptibility as a function of coupling with a peak. Coriolis coupling effects are calculated for the first time; they reduce the susceptibility somewhat.

cond-mat.mtrl-sci↗
arXiv1994

Deformed Hartree-Fock Calculation of Proton-Rich Nuclei

We perform Hartree-Fock+BCS calculations for even-even nuclei with 2 <= Z <= 82 and N ranging from outside the proton drip line to the experimental frontier on the neutron-rich side. The ground state solutions are obtained for 737 nuclei, together with shape-coexistence solutions for 480 nuclei. Our method features the Cartesian-mesh representation of single-particle wavefunctions, which is advantageous in treating nucleon skins and exotic shapes. The results are compared with those of the finite-range droplet model of Moller et al. as well as the experimental values.

nucl-th↗
arXiv1994

Pairing correlation in nuclear matter from Skyrme force

The properties of pairing correlation in nuclear matter are investigated by using various versions of Skyrme forces. Truncation of states involving pairing correlation, necessary due to zero range nature of the Skyrme force, is discussed in detail. A plateau appears in pairing gap versus cutoff for each force. We propose to choose the cutoff parameter in the middle of the plateau so that the parameterization is independent of nuclides.

nucl-th↗