An integrated array of non volatile magnetic memory devices, each having a first magnetic layer (10) with a fixed magnetization direction; a free magnetic layer (20) with a changeable magnetization direction; a spacer layer (30) separating the first magnetic layer and the free magnetic layer, and a switch (40) for selecting the device, the layers and at least part of the switch being formed as a columnar structure such as a nanowire. The switch is preferably formed integrally with the columnar nano-structure. By incorporating the switch in the columnar structure with the magnetic layers, the device can be made smaller to enable greater integration. This can be applied to magnetic devices using external fields or those using only fields generated in the columnar structure. A write current can be coupled along the columnar structure in a forward or reverse direction to alter the direction of magnetization of the free magnetic layer according to the direction of the current.