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A previous polarized neutron reflectivity study of IrMn-based spin valves demonstrated that domain wall formation during training is influenced by the thickness of the ferromagnetic pinned layer. However, magnetoresistance measurements and x-ray reflectivity of spin valves with the same nominal structure revealed that sample roughness may also affect the characteristics of the exchange bias, and thus the type of domain walls that develop. To probe the interplay between structural roughness and domain formation, we measured diffuse neutron scattering from a sample with a thick pinned layer (15 nm) and extracted the field evolution of the in-plane correlation length. At saturation, the correlation length was estimated to be 750 [+ or -]50 nm and originates from magnetic roughness. The correlation length at intermediate fields decreases to 340 nm or less and signifies the formation of in-plane domains. These results suggest that structural roughness enhances the formation of perpendicular domain walls during training. Index Terms--Giant magnetoresistance, magnetic domains, magnetic thin films, spin valves.

Session key exchange has become an addressed topic in the field of communications security, particularly for the IP-based call session that travels through the public network. This paper proposes a hybrid algorithm for session key exchange. The algorithm is designed based on most of the well-proven algorithms, including RSA, D-H, MAC authentication and SHA one-way function, and most of the popular security concepts such as digital signature, digital certificates and verifications under PKI. With an integration of these security concepts and algorithms, the proposed algorithm inherits the properties of these algorithms and realizes highly secure session key exchanging, to meet the required security level of institutions for sensitive communications. It not only improves the possible deficiencies of the algorithms that are singly based on RSA or D-H, but also expands the limits when a hybrid algorithm is applied. Moreover, using MAC codes to ensure the authenticity of the call itself (in addition to ensuring the authenticity of the call parties) meets the communications security concern (in addition to the information security concerns) which relevant algorithms might fail to consider. [ABSTRACT FROM AUTHOR]