This phase II trial studies how well decitabine and total-body irradiation followed by donor bone marrow transplant and cyclophosphamide works in treating patients with relapsed or refractory acute myeloid leukemia. Giving decitabine and total-body irradiation before a donor bone marrow transplant helps stop the growth of cancer cells. It may also stop the patient's immune system from rejecting the donor's stem cells. When the healthy stem cells from a donor are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. Sometimes the transplanted cells from a donor can make an immune response against the body's normal cells. Giving decitabine and total-body irradiation before the transplant together with high-dose cyclophosphamide, tacrolimus, and mycophenolate mofetil after the transplant may stop this from happening.