Magnetic structures of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>PrMn</mml:mi><mml:mn>7</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>12</mml:mn></mml:msub></mml:mrow></mml:math

We report on the magnetic structures of <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>PrMn</a:mi><a:mn>7</a:mn></a:msub><a:msub><a:mi mathvariant="normal">O</a:mi><a:mn>12</a:mn></a:msub></a:mrow></a:math>, resolving both a high-temperature structure in common with the other <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:msup><c:mi>R</c:mi><c:mrow><c:mn>3</c:mn><c:mo>+</c:mo></c:mrow></c:msup><c:msub><c:mi>Mn</c:mi><c:mn>7</c:mn></c:msub><c:msub><c:mi mathvariant="normal">O</c:mi><c:mn>12</c:mn></c:msub></c:mrow></c:math> systems and an additional low-temperature phase characterized by a superposed incommensurate (ICM) spin canting. A phenomenological model is developed to account for large magnetoelastic coupling immediately below the Curie temperature, demonstrating that <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:msup><e:mi>A</e:mi><e:mo>′</e:mo></e:msup><e:mi>B</e:mi></e:mrow></e:math> exchange is primarily responsible for the ferrimagnetic structures observed across the <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"><f:mrow><f:msup><f:mi>R</f:mi><f:mrow><f:mn>3</f:mn><f:mo>+</f:mo></f:mrow></f:msup><f:msub><f:mi>Mn</f:mi><f:mn>7</f:mn></f:msub><f:msub><f:mi mathvariant="normal">O</f:mi><f:mn>12</f:mn></f:msub></f:mrow></f:math> family. Finally, an analytical mean-field minimal model is presented that successfully accounts for all magnetic structures observed in this family of materials, including the canted commensurate and ICM ground states. Published by the American Physical Society 2024