Single orthorhombic b axis orientation and antiferromagnetic ordering type in multiferroic CaMnO₃ thin film with La_0.67Ca_0.33MnO₃ buffer layer Available to Purchase

The detailed crystal structure and antiferromagnetic properties of a 42 nm thick CaMnO₃ film grown on a LaAlO₃ substrate with a 9 nm La_0.67Ca_0.33MnO₃ buffer layer have been investigated. Compared with a CaMnO₃ film directly grown on a LaAlO₃ substrate, only one kind of orthorhombic b axis orientation along the [100] axis of the substrate is observed in the CaMnO₃ film with a La_0.67Ca_0.33MnO₃ buffer layer. To determine the antiferromagnetic ordering type of our CaMnO₃ film with a buffer layer, the first-principles calculations were carried out with the results, indicating that the CaMnO₃ film, even under a tensile strain of 1.9%, is still a compensated G-type antiferromagnetic order, the same as the bulk. Moreover, the exchange bias effect is observed at the interface of the CaMnO₃/La_0.67Ca_0.33MnO₃ film, further confirming the antiferromagnetic ordering of the CaMnO₃ film with a buffer layer. In addition, it is concluded that the exchange bias effect originates from the spin glass state at the La_0.67Ca_0.33MnO₃/CaMnO₃ interface, which arises from a competition between the double-exchange ferromagnetic La_0.67Ca_0.33MnO₃ and super-exchange antiferromagnetic CaMnO₃ below the spin glass freezing temperature.