Reentrant Spin Glass and Magnetic Skyrmions in the Co₇Zn₇Mn_{_6−<i>x</i>}Fe_<i>x</i> <i>β</i>-Mn-Type Alloys

• Published in: Magnetochemistry
• Main Authors: José F. Malta, Marta S. C. Henriques, José A. Paixão, António P. Gonçalves
• Format: Article
• Language: English
• Published: MDPI AG 2024-08-01
• Subjects: <i>β</i>-Mn-type alloys; skyrmions; reentrant spin glass
• Online Access: https://www.mdpi.com/2312-7481/10/8/61
• ISSN: 2312-7481

Co₇Zn₇Mn₆ is a <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>β</mi></semantics></math></inline-formula>-Mn-type alloy belonging to the Co_<i>x</i>Zn_<i>y</i>Mn_<i>z</i> (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>x</mi><mo>+</mo><mi>y</mi><mo>+</mo><mi>z</mi><mo>=</mo><mn>20</mn></mrow></semantics></math></inline-formula>) family that notoriously features a skyrmionic magnetic phase below the ferromagnetic ordering temperature and, in addition, a reentrant spin glass transition at low temperatures. In this work, we have studied the effect of partial substitution of Mn by Fe in the magnetic properties of this alloy. Samples of Co₇Zn₇Mn_6−<i>x</i>Fe_<i>x</i>, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mn>0</mn><mo>≤</mo><mi>x</mi><mo>≤</mo><mn>1</mn></mrow></semantics></math></inline-formula>, were synthesised using the Bridgman–Stockbarger method, and their structure and composition were fully characterised by XRD and EDS. VSM and AC susceptibility measurements show that the partial substitution of Mn by Fe increases <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>T</mi><mi mathvariant="normal">C</mi></msub></semantics></math></inline-formula> and the skyrmionic region of the magnetic phase diagram is suppressed for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>x</mi><mo>></mo><mn>0.5</mn></mrow></semantics></math></inline-formula>. The AC susceptibility behaviour at low temperatures can be ascribed to the presence of a reentrant spin glass state observed for all compositions, with a spin glass freezing temperature, <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>T</mi><mi mathvariant="normal">g</mi></msub></semantics></math></inline-formula>, that shifts to lower temperatures as the Fe content increases.