Reduction of read gap length by thin exchange bias layer

For the material design of antiferromagnetic layer enabling to reduce the read gap length of magnetic recording heads, the exchange bias between the ferromagnetic (FM) and antiferromagnetic (AFM) bilayer was investigated within the framework of the classical Heisenberg model. The dependence of the exchange bias on the AFM layer thickness was also calculated using the Landau-Lifshitz-Gilbert equation. The triple-Q (3Q), T1, and AF-I spin structures are obtained in the disordered 7-phase, ordered L1_2-, and L1_0- type lattices, respectively. The exchange bias is caused by the formation of the interfacial domain wall in the AFM layer, and the critical thickness d_c of the AFM layer is dominated by the varied spin structures. Consequently, the relation of the critical thickness can be represented as √3d_c^3q = √2d_c ^T1 = √_c^AF-I.