According to one embodiment, a TMR effect element includes a ground layer, an antiferromagnetic layer above the ground layer, a first ferromagnetic layer above the antiferromagnetic layer and exchange-coupled to the antiferromagnetic layer, an anti-parallel coupling layer above the first ferromagnetic layer, a second ferromagnetic layer having a magnetic moment coupled anti-parallel to the magnetic moment of the first ferromagnetic layer via the anti-parallel coupling layer, an insulation barrier layer above the second ferromagnetic layer, and a third ferromagnetic layer above the insulation barrier layer. At least a portion of the second ferromagnetic layer and at least a portion of the third ferromagnetic layer on an insulation barrier layer side are comprised of a crystal, and the insulation barrier layer comprises MgO and an oxide material having an independent cubic crystal structure and complete solid solubility with MgO. Other elements, heads, and formation methods are described according to various embodiments.