材料期刊网

We investigate the dynamic hysteresis of nanoscale magnetic aggregates by employing Monte Carlo simulation, based on Ising model in non-integer dimensional space. The diffusion-limited aggregation (DLA) model with adjustable sticking probability is used to generate magnetic aggregates with different fractal dimension D. It is revealed that the exponential scaling law A(H(0), omega)similar to H(0)(alpha).omega(beta), where A is the hysteresis area, H(0) and omega the amplitude and frequency of external magnetic field, applies to both the low-omega and high-omega regimes, while exponents alpha and beta decrease with increasing D in the low-omega regime and keep invariant in the high-omega regime. A mean-field approach is developed to explain the simulated results. (C) 2009 Elsevier B.V. All rights reserved.