The Effect Of Surface And Interface On Neel Transition Temperature Of Low-dimensional Antiferromagnetic Materials

Magnetic materials have attracted much attention recently because of their potential applications in numerous fields such as Electrommunication and National Defense Science and Technology. And low-dimensional materials also have been widely studied because of their novel physical properties which can hardly be seen from their bulk. Therefore, the study and analysis of magnetic nanomaterials are very important to science, technology and our life. We take the antiferromagnetic transition temperature(Neel Transition Tempertaure) as the research object in this text, analysing and exploring the surface and interface effect and the size depend on low-dimensional antiferromagnetic materials. The Neel transition is related to the atomic cohesive/exchange energy that is lowered by the coordination number imperfection of the lower coordinated atoms near the surface edge and changed for depositing on different epitaxial interface. A numerical match between predictions and measurements for a number of specimens reveals that the antiferromagnetic Neel Transition Tempertaure(TN) suppression with size reduced and TN increased with the strengthen of heterogeneous bond and increase of the bond number compared with the bulk.Incorporating the bond order-length-strength notion to the Ising premise and Briluion function, we have modeled the size dependence of the TN of antiferromagnetic nanocrystals. Reproduction of the size trends revealed that surface atomic undercoordination induced bond contraction and interfacial hetero-coordination induced bond nature alteration, which modulated modulate the TN by adjusting the atomic cohesive energy.It is found that the size-induced ΔTN(K)/TN(∞) for the single metal and metallic oxide follow the same rule based on surface effect and interface effect. Consistency between the theory predictions and the measured data about size dependence of the ΔTN(K)/TN(∞) clarify that:(i) the Neel transition temperature is intrinsically proportional to the mean exchange energy of atoms, which can be combined with BOLS notation.(ii) the change in exchange energy due to atom under-coordination and mix-match depress the TN because of the point defects, surface skins, and nanocrystals.(iii) the size induced trend is determined by the ratio of the skin to-body volume and the interface to-body volume. We must pay attention to the importance of the surface and interface for low-dimensional systems.In this study, we establish an analytical method to shed light on the relationship between TN change and the interface effect in epitaxial layers from the perspective of BOLS consideration. Consistency between the theory predicted results and experimental data not only verified our theoretical expectations and numerical approaches but also provide straight forward insight into the mechanism behind the thermal stability of nanostructures. Indeed, it provides ours a new way and could guide us through the choice of different material base to improve the interface for the performance of the materials we need.