Effect of buffer layer on antiferromagnetic grain size and exchange-coupling field of Cr₇₀Al₃₀/Fe₁₉Ni ₈₁ bilayers

MgO/Cr₇₀Al₃₀/FC₁₉Ni₈₁ and ZnO/Cr₇₀Al₃₀/Fe₁₉Ni₈₁ layered films with different buffer layer thicknesses were prepared on (100)Si substrates in order to investigate the relationship among the exchange-coupling field, the grain size, and the lattice constant of the antiferromagnetic layer. The exchange-coupling field was found to consist of the intragrain exchange coupling and the intergrain coupling fields. The former field is inversely proportional to the product of the lattice constant and the grain size. The latter field is constant and changes its sign in association with the increase of the buffer layer thickness.