A data read/write device according to an example of the present invention includes a recording layer, and means for applying a voltage to the recording layer, generating a resistance change in the recording layer, and recording data. The recording layer is composed of a composite compound having at least two types of cation elements, at least one type of the cation element is a transition elementhaving a d orbit in which electrons have been incompletely filled, and the shortest distance between the adjacent cation elements is 0.32 nm or less.