Interfacial Uncompensated Antiferromagnetic Spins: Role in Unidirectional Anisotropy in Polycrystalline <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>Ni</mi></mrow><mrow><mn>81</mn></mrow></msub></mrow><mrow><msub><mrow><mi>Fe</mi></mrow><mrow><mn>19</mn></mrow></msub></mrow><mi>/</mi><mi>CoO</mi></math></span> Bilayers

Kentaro Takano; R. H. Kodama; A. E. Berkowitz; W. Cao; G. Thomas

doi:10.1103/PhysRevLett.79.1130

Interfacial Uncompensated Antiferromagnetic Spins: Role in Unidirectional Anisotropy in Polycrystalline ${Ni}_{81} {Fe}_{19} / CoO$ Bilayers

Kentaro Takano, R. H. Kodama, A. E. Berkowitz, W. Cao, and G. Thomas

Phys. Rev. Lett. 79, 1130 – Published 11 August 1997

Abstract

The uncompensated spins on the surfaces of antiferromagnetic CoO films exhibit a thermoremanent magnetization after field cooling from $T_{N}$ that has the same temperature dependence as the exchange field of $Ni_{81} Fe_{19} / Co O$ bilayers after field cooling. This suggests that these interfacial uncompensated spins are responsible for unidirectional anisotropy. A model based on a calculation of the density of these interfacial uncompensated spins predicts the correct magnitude of the exchange field, as well as the observed inverse dependence on interfacial grain size.