Quaternary memory device fabricated from a single layer Fe film

A cross-shaped Hall device was fabricated from a single-crystal bcc Fe film having two in-plane magnetic easy axes. When a current pulse is applied to a Au strip patterned on top of the Fe Hall device, multiple domains with two orthogonal magnetization directions form in the Fe Hall device during magnetization reversal. Distributions of such domain that result in four different Hall resistance states can then be obtained by applying appropriate current pulses to the Au strip of the device. The writing of each Hall resistance state is then performed by applying a sequence of current pulses to the Au strip that generate magnetic fields required to achieve a desired domain distribution in the Fe film. Time dependent measurements show remarkably robust temporal stability for all four Hall resistance states. The demonstration of the writing process for the four distinct states in this Fe Hall device by current pulse sequences provides the possibility of realizing a practical room-temperature quaternary memory device in a single ferromagnetic film.