Magnetic random access memory (MRAM) cells are provided. MRAM cell includes a plurality of stacked magnetic tunnel junction (MTJ) devices coupled in serial, and a transistor. The transistor has a gate coupled to a word line, a first terminal coupled to a bit line through the stacked MTJ devices, and a second terminal coupled to a source line. The stacked MTJ devices have different sizes. Each of the stacked MTJ devices includes a free layer, a pinned layer and a barrier layer between the free layer and the pinned layer. The free layers of two adjacent stacked MTJ devices are in direct contact with each other.