Magnetic excitation in the hyperkagome antiferromagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Mn</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mi>RhSi</mml:mi></mml:mrow></mml:math>

In a paramagnetic state of a hyperkagome lattice antiferromagnet <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>RhSi</a:mi></a:mrow></a:math>, magnetic diffuse scattering by magnetic short-range order is observed over a wide temperature range of approximately 500 K above the Néel temperature of 190 K. We have studied the magnetic excitation with a single crystal in a wide energy range from 0.3 to 140 meV by inelastic neutron scattering, where the prominent inelastic neutron-scattering signal is observed at <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi mathvariant="bold">Q</b:mi><b:mo>=</b:mo><b:mo>(</b:mo><b:mn>2</b:mn><b:mo>,</b:mo><b:mn>0</b:mn><b:mo>,</b:mo><b:mn>0</b:mn><b:mo>)</b:mo></b:mrow></b:math>. The inelastic scattering intensity integrated for two of twelve magnon modes leads to a localized magnetic moment of about 5 <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:msub><d:mi>μ</d:mi><d:mi mathvariant="normal">B</d:mi></d:msub></d:math> per Mn site, although the long-range ordered magnetic moment is only 2.61 <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:msub><f:mi>μ</f:mi><f:mi mathvariant="normal">B</f:mi></f:msub></f:math> at 4 K. The result suggests that a large part of the magnetic moment does not order in <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:msub><h:mi>Mn</h:mi><h:mn>3</h:mn></h:msub><h:mi>RhSi</h:mi></h:mrow></h:math>, possibly due to the geometrical spin frustration of the hyperkagome lattice. Published by the American Physical Society 2024