Switching of magnetic domains in a noncollinear antiferromagnet at the nanoscale

Antiferromagnets that display very small stray magnetic fields are ideal for spintronic applications. Of particular interest are noncollinear, chiral antiferromagnets of the type <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>Mn</a:mi> <a:mn>3</a:mn> </a:msub> <a:mi mathvariant="normal">X</a:mi> </a:mrow> </a:math> (X = Sn, Ge), which display a large magnetotransport response that is correlated with their antiferromagnetic ordering. The ability to read out and manipulate this ordering is crucial for their integration into spintronic devices. These materials exhibit a tiny unbalanced magnetic moment such that a large external magnetic field can, in principle, be used to set the material into a single antiferromagnetic domain. However, in thin films of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:mrow> <c:msub> <c:mi>Mn</c:mi> <c:mn>3</c:mn> </c:msub> <c:mi>Sn</c:mi> </c:mrow> </c:math> , we find that such fields induce only a partial magnetic ordering. By detecting two orthogonal in-plane components of the magnetic order vector, we can demonstrate switching along multiple easy axes in <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:msub> <d:mi>Mn</d:mi> <d:mn>3</d:mn> </d:msub> <d:mi>Sn</d:mi> </d:mrow> </d:math> and find that the nonswitchable fraction has a unidirectional anisotropy. Studying the switching at the nanoscale allows us to correlate the pinning behavior to crystal grain boundaries in the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:msub> <e:mi>Mn</e:mi> <e:mn>3</e:mn> </e:msub> <e:mi>Sn</e:mi> </e:mrow> </e:math> nanowire structures.