scholarly journals Computer Simulations of Thermal Switching in Small-Grain Ferromagnets

1998 ◽  
Vol 517 ◽  
Author(s):  
M. A. Novotny ◽  
G. Brown ◽  
P. A. Rikvold
Keyword(s):  
Monte Carlo ◽  
Computer Simulations ◽  
Applied Field ◽  
Monte Carlo Study ◽  
System Size ◽  
Single Domain ◽  
Field Temperature ◽  
Thermal Switching ◽  
Ferromagnetic Particles

AbstractWe present Monte Carlo and Langevin micromagnetic calculations to investigate thermal switching of single-domain ferromagnetic particles. For the Monte Carlo study we place particular emphasis on the probability that the magnetization does not switch by time t, Pnot(t). We find that Pnot(t) has different behaviors in different regimes of applied field, temperature, and system size, and we explain this in terms of different reversal mechanisms that dominate in the different regimes. In the micromagnetic study of an array of Ni pillars, we show that the reversal mode is an ‘outside-in’ mode starting at the perimeter of the array of pillars.

Quantum Monte Carlo Study of Water Molecule: A Preliminary Investigation

2004 ◽  
Vol 57 (12) ◽  
pp. 1229 ◽  
Author(s):  
Nicole A. Benedek ◽  
Irene Yarovsky ◽  
Kay Latham ◽  
Ian K. Snook
Keyword(s):  
Monte Carlo ◽  
Water Molecule ◽  
Quantum Monte Carlo ◽  
Density Functional ◽  
Correlation Energy ◽  
Preliminary Investigation ◽  
Monte Carlo Study ◽  
System Size ◽  
Basis Sets ◽  
Advantages And Disadvantages

The Quantum Monte Carlo (QMC) technique[1] offers advantages of good scaling with system size (number of electrons) and an ability to uniformly recover over 90% of the electron correlation energy, compared to the more conventional quantum chemistry approaches. For the water molecule in its ground state, it has been shown[2] that the QMC method gives results that are comparable in accuracy to those obtained by the best available conventional methods, while at the same time using much more modest basis sets than is necessary with these methods. Furthermore, the effect of the orbitals needed for these QMC calculations (which may be obtained from either Hartree–Fock or Density Functional Theory) has been investigated. Both the advantages and disadvantages of the QMC method are discussed.

MICROCANONICAL MONTE CARLO STUDY OF FIRST-ORDER TRANSITION IN A 2D CLASSICAL XY-MODEL

2007 ◽  
Vol 21 (20) ◽  
pp. 3591-3600 ◽  
Author(s):  
SMITA OTA ◽  
SNEHADRI BIHARI OTA
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Study ◽  
System Size ◽  
Order Transition ◽  
Xy Model ◽  
Statistical System ◽  
Simple Method ◽  
First Order ◽  
First Order Transition ◽  
Neighbour Interaction

The microcanonical ensemble given by Boltzmann is used in the computer Monte Carlo simulation of 2D classical XY-model with the modified nearest neighbour interaction potential suggested by Domany, Schick and Swendsen. A relatively simple method to identify first-order transition in computer simulations of a statistical system is described. The critical value of p2 in this XY-model is determined using this method; which is found to increase with system size obeying a power law.

CRITICAL DYNAMICS IN THE 3D SPIN-1/2 HEISENBERG MODEL: A DECOUPLED CELL MONTE CARLO STUDY

1996 ◽  
Vol 07 (03) ◽  
pp. 441-447 ◽  
Author(s):  
CYNTHIA J. SISSON
Keyword(s):  
Monte Carlo ◽  
Quantum Monte Carlo ◽  
Heisenberg Model ◽  
Three Dimensional ◽  
Monte Carlo Study ◽  
System Size ◽  
Classical Heisenberg Model ◽  
Monte Carlo Studies ◽  
Theoretical Predictions ◽  
Good Agreement

The three-dimensional spin-1/2 Heisenberg model on a simple cubic lattice is studied for ferromagnetic and antiferromagnetic interactions using the Decoupled Cell Method for quantum Monte Carlo. Results for the relaxation time τL are determined for both ferromagnetic and antiferromagnetic systems and found to be similar to those found for the classical (s → ∞) Heisenberg model. The scaling of τL with system size is used to extract the dynamical critical exponent z for the two systems. The values of z = 1.98 ± 0.12 for the ferromagnet and z = 1.94 ± 0.09 for the antiferromagnet are in good agreement with theoretical predictions and previous Monte Carlo studies of the classical Heisenberg model.

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