paper

Colossal magnetoresistance in the insulating ferromagnetic double perovskites TlNiMnO: A neutron diffraction study

arXiv:1910.00042 · doi:10.1016/j.actamat.2019.04.044

Abstract

In the family of double perovskites, colossal magnetoresistance (CMR) has been so far observed only in half-metallic ferrimagnets such as the known case SrFeMoO where it has been assigned to the tunneling MR at grain boundaries due to the half-metallic nature. Here we report a new material-TlNiMnO, a relatively ordered double perovskite stablized by the high pressure and high temperature synthesis-showing CMR in the vicinity of its Curie temperature. We explain the origin of such effect with neutron diffraction experiment and electronic structure calculations that reveal the material is a ferromagnetic insulator. Hence the ordered TlNiMnO (~70% of Ni/Mn cation ordering) represents the first realization of a ferromagnetic insulating double perovskite, showing CMR. The study of the relationship between structure and magnetic properties allows us to clarify the nature of spin glass behaviour in the disordered TlNiMnO (~31% of cation ordering), which is related to the clustering of antisite defects and associated with the short-range spin correlations. Our results highlight the key role of the cation ordering in establishing the long range magnetic ground state and lay out new avenues to exploit advanced magnetic materials in double perovskites.

References in corpus (10)