Investigation on a Gap Between Monte Carlo Method and Effective Field Theory in Explaining Magnetocaloric Effect of Metallic Gd Using Ising Model
摘要
Magnetic refrigeration triggers the exploration of excellent magnetocaloric materials (MCMs) from both experimental and theoretical perspectives. The material magnetocaloric effect (MCE) has therefore been studied using the Ising model through Monte Carlo (MC) and effective field theory (EFT) simulations. However, few researchers systematically compare the two simulative results, which can examine the benefits and drawbacks of the two simulation techniques and identify some correlations between the two sets of data. Here, the MCE of Gd was clarified in the Ising model through MC and EFT approaches, where the electronic exchange energy of Gd was 0.82 meV. With the magnetic field varying from 0 to 2 T, the maximal entropy variation and corresponding temperature of Gd, from the MC, EFT simulation, and experimental results, are 5.90 × 104 JK−1 m−3, 4.47 × 104 JK−1 m−3, 4.28 × 104 JK−1 m−3 and 264.4 K, 281.4 K, 294 K, respectively. The maximal entropy variation in the EFT simulation can fit well with the experimental result, which can be explained by the fact that the MC simulation needs larger computational capacity or larger lattice size, and Monte Carlo steps (MCs) can provide more accurate results. In comparison with the MC simulation, the temperature where the largest entropy variation occurs in the EFT simulation is higher, with the field variation from 0 to 2 T. Therefore, the EFT simulation is preferred over the MC simulation when sufficient computational resource is insufficient.