The square-net ferromagnet ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$ has attracted significant attention owing to its zero-field skyrmionic bubbles at room temperature and the associated intriguing topological transport phenomena. Compared with the other members of the $R{\mathrm{Mn}}_2{\mathrm{Ge}}_2$ family ($R$ = rare-earth elements), this compound exhibits a notably more complex and diverse magnetic structure. In this work, we present a systematic investigation of the magnetic properties of ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$. The magnetism predominantly arises from the Mn sublattice across a broad temperature range, with Nd moments becoming significant only at lower temperatures. With increasing external magnetic field applied along the $c$ axis, the ferromagnetic transition temperature $T_{\mathrm{c}}$ shifts to higher temperatures, whereas the spin reorientation temperature $T_{\mathrm{SR}}$ decreases. Based on these observations, we construct a detailed magnetic phase diagram and interpret the field-induced evolution of the topological magnetic states from an energetic standpoint. Critical exponents extracted from isothermal magnetization curves reveal that the magnetic exchange interaction decays as $J\left(r\right)\sim r^{-4.59}$, placing it between short-range and long-range interaction regimes. This intermediate range suggests the coexistence of both interaction types, which may underpin the formation of skyrmionic bubbles in ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$. Furthermore, ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$ exhibits a maximum magnetic entropy change of $4.16\mathrm{J}{\mathrm{kg}}^{-1}{\mathrm{K}}^{-1}$ and a relative cooling power of $218\mathrm{J}{\mathrm{kg}}^{-1}$ at 70 kOe near room temperature. Our results provide a deeper understanding of the magnetic interactions in ${\mathrm{NdMn}}_2{\mathrm{Ge}}_2$ and shed light on the relationship between its complex magnetic behavior and emergent topological spin textures.

Close

PrevNext

View figure in article

• Magnetic phase transitions
• Magnetocaloric effect
• Spin texture
• Ferromagnets
• Critical exponents