Characterizing the diffuse continuum excitations in the classical spin liquid <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:mi>h</mml:mi><mml:mtext>−</mml:mtext><mml:msub><mml:mi>YMnO</mml:mi><mml:mn>3</mml:mn></mml:msub></m

We extend previous inelastic neutron scattering results on the geometrically frustrated antiferromagnet hexagonal-<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:msub><a:mi>YMnO</a:mi><a:mn>3</a:mn></a:msub></a:math>, which has been suggested to belong to the class of classical spin liquids. We expand the energy transfer range of the diffuse signal up to 6.9 meV within a wide temperature range around the ordering temperature, <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:msub><b:mi>T</b:mi><b:mi mathvariant="normal">N</b:mi></b:msub></b:math>. The two distinct diffuse signals in the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mi>a</d:mi><d:mtext>−</d:mtext><d:mi>b</d:mi></d:mrow></d:math> plane, the signal localized at <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:msup><e:mi mathvariant="normal">Γ</e:mi><e:mo>′</e:mo></e:msup></e:math> and the scattering intensity connecting <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:msup><g:mi mathvariant="normal">Γ</g:mi><g:mo>′</g:mo></g:msup></g:math> points over the <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:msup><i:mi mathvariant="normal">M</i:mi><i:mo>′</i:mo></i:msup></i:math>, are shown to be only weakly energy dependent. In addition, an external magnetic field of up to 10.5 T applied along <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"><k:mi>c</k:mi></k:math> is shown to have no effect on the diffuse signal. In the orthogonal scattering plane, the signals are shown to be dependent on <l:math xmlns:l="http://www.w3.org/1998/Math/MathML"><l:mi>l</l:mi></l:math> only through the magnetic form factor, showing that the correlations are purely two-dimensional, and supporting the origin of this to be the frustrated <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:msup><m:mrow><m:mi>Mn</m:mi></m:mrow><m:mrow><m:mn>3</m:mn><m:mo>+</m:mo></m:mrow></m:msup></m:math> triangles. This result is corroborated by atomistic spin dynamics simulations showing similar scattering vector and temperature behaviors. Lastly, data for the spin wave scattering in the <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"><n:mrow><n:mo>(</n:mo><n:mi>h</n:mi><n:mo>,</n:mo><n:mn>0</n:mn><n:mo>,</n:mo><n:mi>l</n:mi><n:mo>)</n:mo></n:mrow></n:math> plane allow for a discussion of the magnetic ground state where better agreement is found between the data and an ordered structure of the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"><o:msub><o:mi mathvariant="normal">Γ</o:mi><o:mn>1</o:mn></o:msub></o:math> or <q:math xmlns:q="http://www.w3.org/1998/Math/MathML"><q:msub><q:mi mathvariant="normal">Γ</q:mi><q:mn>3</q:mn></q:msub></q:math> symmetry, albeit crystal electric field arguments dismiss the <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"><s:msub><s:mi mathvariant="normal">Γ</s:mi><s:mn>1</s:mn></s:msub></s:math> as a possibility. Published by the American Physical Society 2024