Fabrication and study of magnetic competing systems in artificial superlattices

点击翻译按钮获取中文摘要

In this study, fabrication of the magnetic competing, with respect to magnetic antisotropy or exchange-coupling, systems was performed using artificial superlattices. Their magnetic properties were investigated in order to find out novel magnetic phases due to the magnetic competition. The magnetic systems with the competition in magnetic anisotropy were realized in the single-crystal Er/Tb superlattices grown parallel to the c-axis of hcp structure. Neutron diffraction study revealed that, as a function of temperature, the spin component parallel to the c-axis undergoes the same sequence including the Neel and Curie temperatures as bulk Er, while the component in the basal plane retains a helical ordering at higher temperatures up to 130K, which is more than twice the corresponding temperature of bulk Er. We argued that the basal-plane ferromagnetic ordering of the adjacent Tb layers enhanced the development of the basal-plane ordering in the Er layers. In order to study the magnetic systems with the competition in exchange-coupling, fluoride superlattices of FeF_2/ZnF_2 were prepared on single-crystal substrates. In addition to close structural characterization, dependence of the Neel temperature on the thickness of the FeF_2(001) and (110) ultra-thin layers was investigated. The observed periodic variations of the Neel temperature with a period of 1 atomic monolayer were discussed in terms of an interface-topographical frustration due to the competing exchange-coupling of J_2 and J_3. These superlattices can be regarded as "controlled competing systems" in contrast to the bulk dilute system of Fe_xZn_<1-x>F_2.