Applied Physics Letters, 2017, 110, 072405

Zhiyong Quan, Biao Wu, Fei Zhang, Guowei Zhou, Julu Zang, Xiaohong Xu.

Room temperature insulating ferromagnetism induced by charge transferin ultrathin (110) La0.7Sr0.3MnO3 films.

(Appl. Phys. Lett., 2017, 110, 072405 )

Abstract

The achievement of high temperature ferromagnetism in perovskite manganites has proved both fundamentally and technologically important for spintronics devices. However, high operating temperatures have not been achieved due to the depression of the Curie temperature and the rapid spin filtering efficiency loss, which are the main obstacles for practical applications. Here, we report unexpected room temperature insulating ferromagnetism in ultrathin (110) oriented La_0.7Sr_0.3MnO₃ (LSMO) films. The relationships between room temperature ferromagnetism, charge transfer, and orbital occupancy are investigated, with X-ray absorption spectroscopy (XAS) and X-ray linear dichroism (XLD) measurements. Our results suggest that the room temperature insulating ferromagnetism is originated from super-exchange interaction between Mn²⁺ and Mn³⁺. The formation of Mn²⁺ions is related to the charge transfer induced by oxygen vacancies. Moreover, a preferential orbital occupancy of e_g(3z²-r²) in Mn³⁺ ions is crucial to the in-plane super-exchange coupling in ultrathin (110) LSMO films, resulting in insulating ferromagnetic behavior. This work may lead to the development of barrier materials in spin filter tunnel junctions and understanding of ferromagnetic coupling in insulating perovskite films.

全文链接： https://aip.scitation.org/doi/10.1063/1.4976699