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A modified Monte Carlo Metropolis method is performed to simulate the effect of field-cooling strength and interfacial coupling on exchange bias and coercivity of a system with ferromagnetic cores embedded in an antiferromagnetic matrix, based on three-dimensional classical Heisenberg model. The results show that the exchange bias changes from negative value to positive value with increasing cooling field as the interfacial coupling is antiferromagnetic, whereas coercivity is almost unchanged due to the small size of ferromagnetic cores. After applying a weak cooling field, the exchange bias of system with antiferromagnetic interfacial coupling may be positive just when the value of interfacial coupling is not large and exhibit a positive maximum. However, the exchange bias is constantly positive and increasing with increasing values of interfacial coupling after applying a strong cooling field. The exchange bias of system with ferromagnetic interfacial coupling is independent of cooling field and increases for larger interfacial coupling, but the sign is negative due to the constantly positive net magnetization of antiferromagnetic surface. It is obvious that the positive exchange bias depends on the field-cooling strength to a large extent. However, the interfacial coupling may change the configuration of antiferromagnetic matrix to influence the exchange bias.

Spin-wave theory is used to study the effects of interlayer coupling on the properties of layered Heisenberg ferromagnets with S=-. The asymptotic expressions of magnetization and specific heat with temperature and interlayer coupling strength (J, ) are given in two low-temperature regimes distinguished by a characteristic temperature To =2J] /k&. It is shown that the interlayer coupling, though very small, is essential if long-range order at nonzero temperature is to exist.

We report on the experimental and theoretical studies of cooling field (HFC) and temperature (T) dependent exchange bias (EB) in FexAu1 − x/Fe19Ni81 spin glass (SG)/ferromagnet (FM) bilayers. When x varies from 8% to 14% in the FexAu1 − x SG alloys, with increasing T, a sign-changeable exchange bias field (HE) together with a unimodal distribution of coercivity (HC) are observed. Significantly, increasing in the magnitude of HFC reduces (increases) the value of HE in the negative (positive) region, resulting in the entire HE ∼ T curve to move leftwards and upwards. In the meanwhile, HFC variation has weak effects on HC. By Monte Carlo simulation using a SG/FM vector model, we are able to reproduce such HE dependences on T and HFC for the SG/FM system. Thus this work reveals that the SG/FM bilayer system containing intimately coupled interface, instead of a single SG layer, is responsible for the novel EB properties.