Concurrent Modeling of Magnetic Field Parameters, Crystalline Structures, and Ferromagnetic Dynamic Critical Behavior Relationships

Yongyut Laosiritaworn,Wimalin Laosiritaworn 한국자기학회 2014 Journal of Magnetics Vol.19 No.4

In this work, Artificial Neural Network (ANN) was used to model the dynamic behavior of ferromagnetic hysteresis derived from performing the mean-field analysis on the Ising model. The effect of field parameters and system structure (via coordination number) on dynamic critical points was elucidated. The Ising magnetization equation was drawn from mean-field picture where the steady hysteresis loops were extracted, and series of the dynamic critical points for constructing dynamic phase-diagram were depicted. From the dynamic critical points, the field parameters and the coordination number were treated as inputs whereas the dynamic critical temperature was considered as the output of the ANN. The input-output datasets were divided into training, validating and testing datasets. The number of neurons in hidden layer was varied in structuring ANN network with highest accuracy. The network was then used to predict dynamic critical points of the untrained input. The predicted and the targeted outputs were found to match well over an extensive range even for systems with different structures and field parameters. This therefore confirms the ANN capabilities and indicates the ANN ability in modeling the ferromagnetic dynamic hysteresis behavior for establishing the dynamic-phase-diagram.

Monte Carlo Investigation of the Grain-size Dependence of Hysteresis Properties

Yongyut Laosiritaworn 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Monte Carlo Investigation of Spatially Adaptable Magnetic Behavior in Stretchable Uniaxial Ferromagnetic Monolayer Film

Yongyut Laosiritaworn,Wimalin Laosiritaworn 한국자기학회 2015 Journal of Magnetics Vol.20 No.1

In this work, Monte Carlo simulation was employed to model the stretchable Ising monolayer film to investigate the effect of the spatial distance variation among magnetic atoms on magnetic behavior of the film. The exchange interaction was considered as functions of initial interatomic distance and the stretched distance (or the strain). Following Bethe-Slater picture, the magnetic exchange interaction took the Lennard-Jones potential-like function. Monte Carlo simulations via the Wolff and Metropolis algorithms were used to update the spin systems, where equilibrium and dynamic magnetic profiles were collected. From the results, the strain was found to have strong influences on magnetic behavior, especially the critical behavior. Specifically, the phase transition point was found to either increase or decrease depending on how the exchange interaction shifts (i.e. towards or away from the maximum value). In addition, empirical functions which predict how the critical temperatures scale with initial interatomic distance and the strain were proposed, which provides qualitatively view how to fine tune the magnetic critical point in monolayer film using the substrate modification induced strain.

Artificial Neural Network Modeling of Monte Carlo and Mean-field Ising Hysteresis

Wimalin Laosiritawom,Yongyut Laosiritaworn 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Hysteresis Scaling in Exchange Bias System

Sukrit Sucharitakul,Yongyut Laosiritaworn 한국자기학회 2008 한국자기학회 학술연구발표회 논문개요집 Vol.- No.-

Dielectric and ferroelectric properties of 0.8PZT–0.2PCN ceramics under sintering conditions variation

Anurak Prasatkhetragarn,Muangjai Unruan,Athipong Ngamjarurojana,Yongyut Laosiritaworn,Supon Ananta,Rattikorn Yimnirun,David P. Cann 한국물리학회 2009 Current Applied Physics Vol.9 No.5

The influences of sintering conditions on electrical properties of the 0.8Pb(Zr1/2Ti1/2)O3–0.2Pb(Co1/3Nb2/ 3)O3 ceramics have been investigated with sintering temperatures of 1175, 1200, 1225, and 1250 ℃ and dwell times for 2, 6, and 10 h. The crystal structure of dense specimens showed coexistence between tetragonal, rhombohedral and pseudo cubic phases in all sintering temperatures, while tetragonal-rich phase appeared with increasing dwell times. A maximum dielectric constant was observed at sintering condition of 1200 ℃ for 2 h, while the transition temperature slightly increased with increasing dwell time. All ceramics also showed diffused phase transition behaviors with a minimum diffusivity at sintering condition of 1200 ℃ for 2 h. In addition, the polarization–electric field (P–E) hysteresis loops of the ceramic systems also changed significantly with sintering conditions. Interestingly, the ferroelectric parameters; remnant polarization (Pr) and loop squareness (Rsq) tended to increase with increasing sintering temperatures and dwell times. The influences of sintering conditions on electrical properties of the 0.8Pb(Zr1/2Ti1/2)O3–0.2Pb(Co1/3Nb2/ 3)O3 ceramics have been investigated with sintering temperatures of 1175, 1200, 1225, and 1250 ℃ and dwell times for 2, 6, and 10 h. The crystal structure of dense specimens showed coexistence between tetragonal, rhombohedral and pseudo cubic phases in all sintering temperatures, while tetragonal-rich phase appeared with increasing dwell times. A maximum dielectric constant was observed at sintering condition of 1200 ℃ for 2 h, while the transition temperature slightly increased with increasing dwell time. All ceramics also showed diffused phase transition behaviors with a minimum diffusivity at sintering condition of 1200 ℃ for 2 h. In addition, the polarization–electric field (P–E) hysteresis loops of the ceramic systems also changed significantly with sintering conditions. Interestingly, the ferroelectric parameters; remnant polarization (Pr) and loop squareness (Rsq) tended to increase with increasing sintering temperatures and dwell times.

Effects of Zr/Ti ratio on dielectric and ferroelectric properties of 0.8Pb(ZrxTi1-x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics

Anurak Prasatkhetragarn,Muangjai Unruan,Athipong Ngamjarurojana,Yongyut Laosiritaworn,Supon Ananta,Rattikorn Yimnirun,David P. Cann 한국물리학회 2009 Current Applied Physics Vol.9 No.4

The influences of Zr/Ti ratio on electrical properties of the 0.8Pb(ZrxTi1-x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics prepared by a mixed-oxide method (with x = 0.46, 0.48, 0.50, 0.52, and 0.54) have been investigated in order to identify the morphotropic phase boundary composition in this system. With XRD analysis, the crystal structure of dense specimens appeared to change gradually from tetragonal to rhombohedral with increasing Zr content. The dielectric properties measurements showed a maximum dielectric constant at x = 0.50, while the transition temperature decreased with increasing Zr content in the system. Moreover, all ceramics showed diffused phase transition behaviors with a minimum diffusivity at x = 0.50. In addition, the Polarization–Electric field (P–E) hysteresis loops of the ceramic systems also changed significantly with the Zr content. Interestingly, the loop squareness parameter reached maximum around x = 0.50. Other ferroelectric hysteresis parameters showed noticeable change at x = 0.50. These results clearly showed the significance of Zr/Ti ratio in controlling the electrical properties of the PZT–PCN ceramic systems. The influences of Zr/Ti ratio on electrical properties of the 0.8Pb(ZrxTi1-x)O3–0.2Pb(Co1/3Nb2/3)O3 ceramics prepared by a mixed-oxide method (with x = 0.46, 0.48, 0.50, 0.52, and 0.54) have been investigated in order to identify the morphotropic phase boundary composition in this system. With XRD analysis, the crystal structure of dense specimens appeared to change gradually from tetragonal to rhombohedral with increasing Zr content. The dielectric properties measurements showed a maximum dielectric constant at x = 0.50, while the transition temperature decreased with increasing Zr content in the system. Moreover, all ceramics showed diffused phase transition behaviors with a minimum diffusivity at x = 0.50. In addition, the Polarization–Electric field (P–E) hysteresis loops of the ceramic systems also changed significantly with the Zr content. Interestingly, the loop squareness parameter reached maximum around x = 0.50. Other ferroelectric hysteresis parameters showed noticeable change at x = 0.50. These results clearly showed the significance of Zr/Ti ratio in controlling the electrical properties of the PZT–PCN ceramic systems.

Ferroelectric properties of Pb(Zr1/2Ti1/2)O3–Pb(Zn1/3Nb2/3)O3 ceramics under compressive stress

Rattikorn Yimnirun,Narit Triamnak,Muangjai Unruan,Athipong Ngamjarurojana,Yongyut Laosiritaworn,Supon Ananta 한국물리학회 2009 Current Applied Physics Vol.9 No.1

Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1-x)Pb(Zr1/2Ti1/2)O3–xPb(Zn1/3Nb2/3)O3 or (1-x)PZT–(x)PZN (x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (Psat), the remnant polarization (Pr), and the coercive field (Ec) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes. Effects of compressive stress on the ferroelectric properties of ceramics in PZT–PZN system were investigated. The ceramics with a formula (1-x)Pb(Zr1/2Ti1/2)O3–xPb(Zn1/3Nb2/3)O3 or (1-x)PZT–(x)PZN (x = 0.1–0.5) were prepared by a conventional mixed-oxide method. The ferroelectric properties under the compressive stress of the PZT–PZN ceramics were observed at the stress levels up to 170 MPa using a compressometer in conjunction with a modified Sawyer–Tower circuit. It was found that with increasing compressive stress the area of the ferroelectric hysteresis (P–E) loops, the saturation polarization (Psat), the remnant polarization (Pr), and the coercive field (Ec) decreased. These results were interpreted through the non-180° ferroelastic domain switching processes.