Increased neutron reflectivity and polarization of neutron-optical engineered Fe/B411CTi multilayer optics

The concept of scattering length density tuning for improved polarization is investigated for Fe/<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mmultiscripts><a:mi mathvariant="normal">B</a:mi><a:mn>4</a:mn><a:none/><a:mprescripts/><a:none/><a:mn>11</a:mn></a:mmultiscripts><a:mi>CTi</a:mi></a:mrow></a:math> multilayers and compared to the commonly used Fe/Si system in polarizing multilayer neutron optics. X-ray and neutron reflectivity, magnetization, and neutron polarization were measured on such multilayers, highlighting differences from conventional Fe/Si multilayers. The multilayer systems were deposited with 25 Å period thickness, a layer thickness ratio of 0.35, and 20 periods using ion-assisted dc magnetron sputtering. Replacing Si with <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mmultiscripts><c:mi mathvariant="normal">B</c:mi><c:mn>4</c:mn><c:none/><c:mprescripts/><c:none/><c:mn>11</c:mn></c:mmultiscripts><c:mi>CTi</c:mi></c:mrow></c:math> for these multilayers showed an increase in reflectivity due to a reduction in interface width. Tuning the ratio between <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mmultiscripts><e:mi mathvariant="normal">B</e:mi><e:mn>4</e:mn><e:none/><e:mprescripts/><e:none/><e:mn>11</e:mn></e:mmultiscripts><e:mi mathvariant="normal">C</e:mi></e:mrow></e:math> and Ti in the nonmagnetic layers enabled a wide range of scattering length density contrasting and matching for spin-down neutrons, which in turn led to an improved polarization. These findings demonstrate the potential of Fe/<h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mmultiscripts><h:mi mathvariant="normal">B</h:mi><h:mn>4</h:mn><h:none/><h:mprescripts/><h:none/><h:mn>11</h:mn></h:mmultiscripts><h:mi>CTi</h:mi></h:mrow></h:math> multilayers as a promising option for polarizing neutron optics and highlight the concept of scattering length density tuning in a large range using <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"><j:mrow><j:mmultiscripts><j:mi mathvariant="normal">B</j:mi><j:mn>4</j:mn><j:none/><j:mprescripts/><j:none/><j:mn>11</j:mn></j:mmultiscripts><j:mi>CTi</j:mi></j:mrow></j:math>.