Success of a simulation approach for magnetic nanosystems: Power of physical laws

• Our new quantum simulation method was successfully applied to a ferromagnetic nanowire.
• To verify the correctness of the new approach, all simulations were started from a random magnetic configuration.
• The total free energies of the nanosystem were found to decrease spontaneously in simulations.
• So our hypothesis that the new approach is built on the principle of lowest free energy is proved.
• Using the new approach, the computing speed may be considerably accelerated.

The new quantum simulation model and the self-consistent algorithm (SCA) for magnetic nanosystems, that we proposed 2 years ago, were extended to study the magnetic properties of a nanowire consisting of 3d ions which are coupled ferromagnetically. To test the applicability of the algorithm, our simulations in the present work were started from a magnetic structure in which all spins in the whole nanosample were randomly oriented (defined as the random magnetic configuration for later use) as other authors have been doing with Monte Carlo or micromagnetism method, and such calculated results were all reasonable. Especially, the free energies evaluated at the chosen temperatures were found to attenuate spontaneously and quickly, as the program ran, towards the minima according to the principle of lowest free energy as expected. This suggests that the computational algorithm is able to lead the code to converge rapidly to the equilibrium state automatically without the need to minimize the total (free) energy of the system elaborately that must be done if the Monte Carlo or micromagnetism method is used, demonstrating the great power of natural laws.