Ferrimagnetic structure in the high-pressure phase of α−Mn

The <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>α</a:mi><a:mtext>−</a:mtext><a:mi>Mn</a:mi></a:mrow></a:math> phase exhibits a large anomalous Hall effect (AHE) in its pressure-induced weak ferromagnetic (WFM) state, despite its relatively small spontaneous magnetization of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mo>∼</b:mo><b:mn>0.02</b:mn><b:mspace width="0.222222em"/><b:msub><b:mi>μ</b:mi><b:mi mathvariant="normal">B</b:mi></b:msub><b:mo>/</b:mo><b:mi>Mn</b:mi></b:mrow></b:math>. To understand the underlying mechanism behind this AHE, we performed single crystal neutron diffraction measurements at 2.0 GPa to determine the magnetic structure of the WFM phase. Our investigation reveals a ferrimagnetic structure characterized by nearly collinear magnetic moments aligned along the [001] direction at sites I, II, III-1, and IV-1. In contrast, the small moments at sites III-2 and IV-2 lie within the (001) plane. The calculated net magnetization of this magnetic structure, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mrow><e:mo>(</e:mo><e:mo>−</e:mo><e:mn>0.08</e:mn><e:mo>±</e:mo><e:mn>0.10</e:mn><e:mo>)</e:mo></e:mrow><e:mspace width="0.222222em"/><e:msub><e:mi>μ</e:mi><e:mi mathvariant="normal">B</e:mi></e:msub><e:mo>/</e:mo><e:mi>Mn</e:mi></e:mrow></e:math> atom, is in agreement with the experimentally determined spontaneous magnetization. The observation of a magnetic reflection at <h:math xmlns:h="http://www.w3.org/1998/Math/MathML"><h:mrow><h:mi mathvariant="bold-italic">q</h:mi><h:mo>=</h:mo><h:mo>(</h:mo><h:mn>0</h:mn><h:mo>,</h:mo><h:mn>0</h:mn><h:mo>,</h:mo><h:mn>0</h:mn><h:mo>)</h:mo></h:mrow></h:math> satisfies a key condition for the emergence of the AHE. Published by the American Physical Society 2024