Interplay of magnetocrystalline and magnetoelastic anisotropy in epitaxial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>Co</mml:mi><mml:mo>(</mml:mo><mml:mn>10</mml:mn><mml:mover accent="true"><mml:mn>1</mml:mn><mml:mo>¯

With the goal of creating an in-plane (IP) uniaxial anisotropy system, we deposited a thickness series of epitaxial <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>Co</a:mi><a:mo>(</a:mo><a:mn>10</a:mn><a:mover accent="true"><a:mn>1</a:mn><a:mo>¯</a:mo></a:mover><a:mn>0</a:mn><a:mo>)</a:mo></a:mrow></a:math> films grown on Si(110) substrates with Ag(110) and Cr(211) buffer layers by magnetron sputtering. However, quantifying the IP magnetic anisotropy using ferromagnetic resonance measurements revealed a much more complex behavior than expected for a simple uniaxial system like hexagonally close-packed (hcp) Co. To understand the experimental results, an in-depth x-ray diffraction analysis of the film structure was performed. Even at a thickness of 100 nm, it revealed an anisotropic strain in the Co films, mainly within the Co basal plane, while the <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mi>c</c:mi></c:math> axis remained mostly unaffected. Calculations show that such unrelaxed strain induces a significant magnetoelastic anisotropy, which counteracts the magnetocrystalline one and, as a result, reduces the overall effective anisotropy. A detailed analysis revealed that mainly the compressive strain along the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mi>Co</d:mi><d:mo>[</d:mo><d:mn>10</d:mn><d:mover accent="true"><d:mn>1</d:mn><d:mo>¯</d:mo></d:mover><d:mn>0</d:mn><d:mo>]</d:mo></d:mrow></d:math> out-of-plane direction is responsible for the observed magnetoelastic anisotropy, while the tensile strain along the <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:mi>Co</f:mi><f:mo>[</f:mo><f:mover accent="true"><f:mn>1</f:mn><f:mo>¯</f:mo></f:mover><f:mn>2</f:mn><f:mover accent="true"><f:mn>1</f:mn><f:mo>¯</f:mo></f:mover><f:mn>0</f:mn><f:mo>]</f:mo></f:mrow></f:math> IP direction only plays a minor role.