Search

Recently antiferromagnetic materials become very attractive due to their new applications in spintronic devices. High-quality single crystal epitaxial ZnxCo1−xO (1 1 1) thin films were grown by co-evaporating Zn and Co and simultaneously oxidizing in oxygen plasma. It is found that the exchange bias fields of Co/as-prepared ZnxCo1−xO bilayers decrease with increasing Zn composition. When as-prepared ZnxCo1−xO layer was annealed in oxygen plasma to remove oxygen vacancies, the exchange bias field of Co/oxygen-plasma-annealed ZnxCo1−xO bilayers can be further enhanced. Moreover, a weak ferromagnetism was observed at 300 K in the as-prepared antiferromagnetic ZnxCo1−xO film with oxygen vacancies, but it did not exist in oxygen-plasma-annealed ZnxCo1−xO film. This indicates that oxygen vacancies can simultaneously weaken the antiferromagnetism but enhance the ferromagnetism of ZnxCo1−xO layer. Therefore, we offer a method of manipulating the antiferromagnetism of ZnxCo1−xO films by changing Zn composition and oxygen vacancies, which is useful for designing antiferromagnetic spintronic devices.

High performance of many spintronic devices strongly depends on the spin-polarized electrical transport, especially the magnetoresistance (MR) in magnetic heterojunctions. However, it has been a great challenge to distinguish the bulk MR and interface MR by transport measurements because the bulk resistance and interface resistance formed a series circuit in magnetic heterojunctions. Here, a unique interface-sensitive rectification MR method is proposed to distinguish the interface MR and bulk MR of nonmagnetic In/GeOx/n-Ge and magnetic Co/GeOx/n-Ge diode-like heterojunctions. It is demonstrated that the low-field “butterfly” hysteresis loop observed only in the conventional MR curve originates from the anisotropic MR of ferromagnetic bulk Co layer, whereas the orbit-related large nonsaturating positive MR contains contributions from both the Schottky interface and bulk Ge substrate. This rectification MR method could be extended to magnetic heterojunctions with asymmetric potential barriers to realize a ...

Heterostructures consisting of ferromagnetic metal and antiferromagnetic insulator have exhibited novel properties in interface exchange coupling, magnetoresistance and spin injection due to their fundamental physics of magnetism. However, as compared with bilayer heterostructures, it is very challenging in experiments to prepare single crystal epitaxial ultrathin superlattices consisting of ferromagnetic metal and antiferromagnetic insulator, where the interface exchange coupling, magnetic order, and electrical transport properties are expected to be greatly modulated due to the multiple interfaces and periodical structures. Here we prepared single crystal epitaxial [Co/CoO]n superlattices consisting of ferromagnetic metal Co and antiferromagnetic insulator CoO by molecular beam epitaxy. It is found that the saturation magnetization of [Co 0.6 nm/CoO 1.2 nm]5 superlattice is robust against temperature increase, which only shows a slight decrease of 1.5% from 5 K to 300 K. Moreover, we found that the longitudinal resistivity and anomalous Hall resistivity of [Co/CoO]n superlattices are strongly modulated by the short-period Co/CoO heterostructure, which are quite distinguished from the electrical transport properties of Co bulk ferromagnetic metal. The [Co/CoO]n superlattices provide a new insight into heterostructures consisting of ferromagnetic metal and antiferromagnetic insulator, which are beneficial for designing future spintronics devices.