Anomalous Magnetic Evolution in Nd₁₋ₓGdₓSb: Nonmonotonic T_N and Emergent Secondary Transition

The discovery of unconventional surface-state pairs and Fermi arcs in antiferromagnetic NdBi has renewed interest in rare-earth monopnictides, which provide a platform to explore the interplay between magnetism and topology.[1] Recent ARPES and DFT studies on NdSb revealed novel surface band splitting below TN and surface domains associated with different magnetic moment orientations.[2] Different behavior below T_N was found for GdSb.  In addition, whereas for most rare-earth antimonides (RSb) compounds, the Néel temperature (T_N) scales well with the de Gennes factor, NdSb and CeSb are the two exceptions. Motivated by these findings, we synthesized a series of Nd_1-xGd_xSb (0≤x≤1) single crystals and investigated evolution of their structural and magnetic properties. The lattice constant of Nd_1-xGd_xSb decreases linearly with x, following Vegard’s law. As x in increased from 0 to ~0.35 T_N decreases by roughly a factor of two, in stark contrast to de Gennes scaling predictions.  When x > 0.35 in Nd_1-xGd_xSb, T_N again follows the de Gennes scaling remarkably well. For x≥0.35, an additional low-temperature peak appears in the magnetization measurement, suggesting an additional spin-reorientation transition.  The implications of these results will be discussed in light of recent ARPES measurements, and bandstructure calculations.

 

[1] Schrunk, B., et al, Nature 603, 610–615 (2022).

[2] Kushnirenko, Y. et al, Phys. Rev. B 108,115102(2023).