Ordering kinetics in systems with long-range interactions

Long-range magnetic interactions and proximity effects in an amorphous exchange-spring magnet

Low-dimensional magnetic heterostructures are a key element of spintronics, where magnetic interactions between different materials often define the functionality of devices. Although some interlayer exchange coupling mechanisms are by now well established, the possibility of direct exchange coupling via proximity-induced magnetization through non-magnetic layers is typically ignored due to the presumed short range of such proximity effects. Here we show that magnetic order can be induced throughout a 40-nm-thick amorphous paramagnetic layer through proximity to ferromagnets, mediating both exchange-spring magnet behaviour and exchange bias. Furthermore, Monte Carlo simulations show that nearest-neighbour magnetic interactions fall short in describing the observed effects and long-range magnetic interactions are needed to capture the extent of the induced magnetization. The results highlight the importance of considering the range of interactions in low-dimensional heterostructures and how magnetic proximity effects can be used to obtain new functionality.

Ordering kinetics in liquid crystals with long-ranged interactions

We present the results from comprehensive Monte Carlo (MC) simulations of ordering kinetics in d = 2 liquid crystals (LCs). Our LC system is described by the two-component Lebwohl-Lasher model with long-ranged interactions, V(r) ∼ r(-n). We find that systems with n ≥ 2 show the same dynamical behavior as the nearest-neighbor case (n = ∞). This contradicts available theoretical predictions.

Phase ordering kinetics in uniaxial nematic liquid crystals with second- and fourth-rank interactions

We present comprehensive results of the Monte Carlo (MC) simulations of the phase ordering dynamics in d = 2 nematic liquid crystals. We study a system of size N (2)(N = 512) with molecules confined to a 512×512 square lattice and report the results for two LC Hamiltonians: generalized Lebwohl-Lasher (GLL) model and r(-6) dependent anisotropic dispersion interaction potential. In these Hamiltonians a fourth-rank Legendre polynomial P4 interaction term is added to the usual second-rank P2 term. We find that in both the cases the presence of the P4 interaction term significantly influences the nematic domains morphology. Our numerical data show a diffusive growth law with a logarithmic correction: L(t) ∼ (t/ln t)(1/2).