Nagoya-shi, Japan
Nagoya-shi, Japan

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Kaneyoshi T.,Kurosawadai | Kaneyoshi T.,Nagoya University
Journal of Magnetism and Magnetic Materials | Year: 2015

The phase diagram and magnetizations in two transverse Ising nanoislands with the same structures which are consisted of the two layers are examined by using the effective-field theory with correlations. The effects of interlayer coupling and two transverse fields at the center and the perimeter atoms on them are examined. We find remarkable features in them which come from the frustration induced by the interlayer coupling and two transverse fields. © 2014 Elsevier B.V.


Kaneyoshi T.,Kurosawadai | Kaneyoshi T.,Nagoya University
Solid State Communications | Year: 2011

Phase diagrams (transition temperature and compensation temperature) of a cylindrical ferrimagnetic nanotube with a negative coreshell interaction, described by the transverse Ising model (TIM), are investigated by the use of the effective-field theory with correlations. The phase diagrams of the system are strongly affected by the surface dilution. The possibility of two compensation points is found in the phase diagram, in contrast to the case of a cylindrical TIM nanowire. © 2011 Elsevier Inc. All rights reserved.


Kaneyoshi T.,Kurosawadai | Kaneyoshi T.,Nagoya University
Journal of Magnetism and Magnetic Materials | Year: 2011

Initial susceptibility and magnetization of a cylindrical nanotube described by the Ising model are investigated by the use of the effective field theory with correlations (EFT), since the phase diagrams of the system have been examined in the previous work of Kaneyoshi (2010) [8] using the two theoretical frameworks of the mean field theory and the EFT. The effects of the two exchange couplings at the surface shell and in the core to the initial susceptibility are clarified. Some characteristic phenomena are found in the thermal variations, depending on the ratios of the physical parameters in the surface shell and the core. It is also discussed whether the Neel hyperbola in the paramagnetic region is valid for a nano-scaled ferrimagnetic system. © 2011 Elsevier B.V. All rights reserved.


Kaneyoshi T.,Kurosawadai
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2012

The magnetic properties (phase diagram and total magnetization) of a decorated Ising nanowire are examined by the use of the effective field theory with correlations. The system, consisting of spin-1/2 atoms and decorating spin-S (S>1/2) atoms with a crystal-field interaction on the bonds, show ferrimagnetism, compensation point and reentrant behavior. © 2012 Elsevier B.V. All rights reserved.


Kaneyoshi T.,Kurosawadai
Physica B: Condensed Matter | Year: 2015

The phase diagrams, saturation magnetizations and temperature dependences of magnetizations in a transverse Ising nanoisland with an antiferromagnetic spin configuration are studied by the uses of the effective-field theory with correlations (EFT) and the mean-field approximation (MFA), in order to clarify whether the MFA can be successfully applied to the theoretical discussions of naonoislands. From these investigations, we have found a lot of unexpected characteristic phenomena in these properties, when the value of an interlayer coupling takes a large value. We have also found that the applications of the MFA to the magnetic properties are extremely restricted for nanoislands, when the value of an interlayer coupling takes a large value, in contrast to a number of bulk studies. © 2015 Elsevier B.V. All rights reserved.


Kaneyoshi T.,Kurosawadai
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2015

The phase diagrams and temperature dependences of magnetizations in cylindrical Ising nanowire and nanotube are studied by the uses of the effective-field theory with correlations (EFT) and the core-shell concept, where a negative exchange interaction is selected at the surface shell and two positive exchange interactions are taken in the core and between the core and the surface shell. Some unconventional features, such as the possibility of re-entrant phenomena being free from disorder induced frustration, are obtained for the magnetic properties in such systems. © 2015 Elsevier B.V. All rights reserved.


Kaneyoshi T.,Kurosawadai
Physica A: Statistical Mechanics and its Applications | Year: 2012

The phase diagrams (transition temperature and compensation temperature) and magnetizations of a cylindrical nanowire with a (positive or negative) coreshell interaction and a surface dilution, described by the transverse Ising model (TIM), are investigated by the use of the effective-field theory with correlations. The magnetic properties of the system are strongly affected by the surface dilution. In particular, the temperature dependences of magnetizations in the system have shown many characteristic phenomena, depending on the selected physical parameters. © 2012 Elsevier B.V. All rights reserved.


Kaneyoshi T.,Kurosawadai
Physica A: Statistical Mechanics and its Applications | Year: 2013

The phase diagrams and magnetizations of two nanosystems (nanotube and nanowire) with a dilution at the surface are investigated by the use of the effective field theory with correlations. In particular, the effects of interlayer coupling between the surface and the core on them are discussed for the two systems. Some interesting phenomena have been found in the phase diagrams and the thermal variations of magnetizations, especially for the nanotube with a very high dilution and the possibility of two compensation points in the nanowire with a small interlayer coupling. © 2013 Elsevier B.V. All rights reserved.


Kaneyoshi T.,Kurosawadai
Physica Status Solidi (B) Basic Research | Year: 2011

Magnetic properties (phase diagram and magnetization) of a cylindrical Ising nanowire or nanotube are investigated by the use of the effective-field theory with correlations. Particular emphasis is given to the effects of the surface and its dilution on them. Much attention is paid to the thermal variation of the magnetization when the spins at the surface are coupled antiferromagnetically to the ferromagnetic core spins by the negative shell coupling. The effects of dilution at the surface, the surface exchange interaction, and the shell coupling on the magnetization profiles are investigated. We find a number of characteristic phenomena for them. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Kaneyoshi T.,Kurosawadai
International Journal of Modern Physics B | Year: 2015

The phase diagrams and temperature dependences of magnetizations in a transverse Ising bilayer film with an antiferromagnetic spin configuration are studied by the uses of the effective-field theory (EFT) with correlations, in order to clarify whether the appearance of a compensation point is possible below the transition temperature in the system. From these investigations, we have found a lot of characteristic phenomena in these properties, when the value of an interlayer coupling takes a large value, such as the reentrant phenomenon free from the disorder-induced frustration and the novel types of magnetization curve with a compensation point. © 2015 World Scientific Publishing Company.

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