Magnetism of DyNi₂B₂C nanoparticle investigated with a quantum simulation model

Abstract

We employed a quantum simulation model and a new computational algorithm we developed recently to study the magnetism of an assumed DyNi 2 B 2 C nanoparticle consisting of an inner core and an outer shell of complicated crystal and magnetic structures. Our theoretical results obtained with the new simulation model are reasonable physically, and the computational speed with the new algorithm is faster than the micromagnetism and Monte-Carlo approaches, which have been popularly utilized by most researchers worldwide for many years.

A quantum simulation approach for a three-dimensional Ising spin model—Comparison to mean field theory

“…Although the standard treatment is usually very complicated, it turns out that all can be easily managed if one applies the quantum SCA approach. 20 The intricate magnetic anisotropic energy terms in the Hamiltonian would be difficult to manipulate if the large total angular moments of the rare-earth ions (for example, a value of 15/2 for Dy ion in a DyNi 2 B 2 C nanoball) are treated conventionally as classical vectors. In such a case, it is expected that the convergence would be very hard to reach even after a large number of iterations.…”

“…However, our calculations for such a case have shown that the SCA computational program runs smoothly and quickly converges to generate reasonable results. 20 …”

“…For this reason we refer to this method as the SCA approach. [19][20][21][22] The approach is based on the principle of least (free) energy. 19,22 The underlying idea of the treatment is to let all magnetic spin moments of the system adjust themselves relative to the local effective magnetic field in such a way as to spontaneously minimize the total (free) energy of the system at every step of the computational process.…”

“…So far, we successfully applied the SCA approach to study magnetic nanosystems consisting of rare-earth elements 19,20 and 3d transition metals. [21][22][23][24] In particular, the simulated magnetic structure of a DyNi 2 B 2 C nanoball using the SCA approach agrees well with the one observed in the bulk sample.…”

“…The calculations indicated that the transition temperature obtained from simulations is very close to that of the bulk sample. 20 Recently, we employed the SCA approach to investigate the magnetic and thermodynamic properties of FM and AFM spin systems in nanodisks with co-existence of Heisenberg exchange and DzyaloshinskyMoriya interactions. 25 The computational program converged very quickly and generated both FM and the AFM spin vortices on the disk planes with almost perfect symmetry.…”