A magnetic device comprising: - a first magnetic layer called a "reference layer" having a fixed direction magnetisation; - a second magnetic layer called a "storage layer" having a variable direction magnetisation, wherein the magnetisation of the storage layer is orientable either in parallel or in anti-parallel to the magnetisation of the reference layer; - a first spacer separating the reference layer from the storage layer, characterised in that the device further includes: - a third magnetic layer called a "control layer" having a variable direction magnetisation so as to switch the magnetic device from a reading mode to a writing mode and reversely, the magnetisation of the control layer being, prior to any reading or writing, controlled such that: ∘ in reading mode, the control layer has a magnetisation direction respectively parallel or anti-parallel to the magnetisation direction of the reference layer depending on the type of the storage layer (respectively single layer or trilayer) so as to subtract the spin transfer torques exerted by the reference layer and the control layer on the magnetisation of the storage layer; ∘ in writing mode, the control layer has a magnetisation direction: ▪ parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction anti-parallel to the magnetisation direction of the reference layer in reading mode, or ▪ anti-parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction parallel to the magnetisation direction of the reference layer in reading mode; - a second spacer separating the storage layer from the control layer, - means for controlling the magnetisation direction of the control layer able to modify the magnetisation direction of the control layer without modifying the magnetisation direction of the storage layer. - a first magnetic layer called a "reference layer" having a fixed direction magnetisation; - a second magnetic layer called a "storage layer" having a variable direction magnetisation, wherein the magnetisation of the storage layer is orientable either in parallel or in anti-parallel to the magnetisation of the reference layer; - a first spacer separating the reference layer from the storage layer, - a third magnetic layer called a "control layer" having a variable direction magnetisation so as to switch the magnetic device from a reading mode to a writing mode and reversely, the magnetisation of the control layer being, prior to any reading or writing, controlled such that: ∘ in reading mode, the control layer has a magnetisation direction respectively parallel or anti-parallel to the magnetisation direction of the reference layer depending on the type of the storage layer (respectively single layer or trilayer) so as to subtract the spin transfer torques exerted by the reference layer and the control layer on the magnetisation of the storage layer; ∘ in writing mode, the control layer has a magnetisation direction: ▪ parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction anti-parallel to the magnetisation direction of the reference layer in reading mode, or ▪ anti-parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction parallel to the magnetisation direction of the reference layer in reading mode; ∘ in reading mode, the control layer has a magnetisation direction respectively parallel or anti-parallel to the magnetisation direction of the reference layer depending on the type of the storage layer (respectively single layer or trilayer) so as to subtract the spin transfer torques exerted by the reference layer and the control layer on the magnetisation of the storage layer; ∘ in writing mode, the control layer has a magnetisation direction: ▪ parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction anti-parallel to the magnetisation direction of the reference layer in reading mode, or ▪ anti-parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction parallel to the magnetisation direction of the reference layer in reading mode; ▪ parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction anti-parallel to the magnetisation direction of the reference layer in reading mode, or ▪ anti-parallel to the magnetisation direction of the reference layer when the control layer has a magnetisation direction parallel to the magnetisation direction of the reference layer in reading mode; - a second spacer separating the storage layer from the control layer, - means for controlling the magnetisation direction of the control layer able to modify the magnetisation direction of the control layer without modifying the magnetisation direction of the storage layer.