No abstract

The magnetocaloric effect and the universal character for the magnetic entropy change regarding the cubic crystal structures (SC, BCC, FCC) were investigated, in a qualitative way, using Monte Carlo simulations. A classical Heisenberg Hamiltonian with nearest neighbors, and next nearest neighbors interactions was implemented. In order to compute the critical temperature of the system depending on the coordination number, it was calculated the dependence of the magnetization and magnetic susceptibility as a function of temperature. Magnetic field dependence on the magnetization for isothermal processes was performed considering a magnetocrystalline anisotropy term. In this way, the magnetic entropy change (Δ S m ) was computed. Results show that the rescaled Δ S m as well as the exponent ( n ) characterizing the field dependence of the magnetic entropy change curves, collapse onto a single curve for the studied crystal structures. By this reason, it can be assured that Δ S m exhibits a universal behavior regarding the strength and contribution of the magnetic exchange energy to the total magnetic energy.

We provide a guide to implementing the particle-in-cell algorithm, which is useful for simulating diverse phenomena in plasmas. We focus on two-dimensional systems which have vector fields with three Cartesian components but depend only on two spatial coordinates. We describe the algorithm in detail, including particle-to-grid interpolation, the fast Fourier transform, the Boris algorithm, and the use of dimensionless units. As an example, we discuss a simulation of the two-stream instability, which occurs in a plasma system composed of two counter-streaming electrons and an ion background at rest.