Unusual First-Order Antiferromagnetic Transitions

Scientific Achievement

First-order transitions were observed at the antiferromagnetic transition temperatures of CaMn2P2 and SrMn2P2 crystals with corrugated honeycomb Mn layers.

heat capacity v. temp
Heat Capacity Cp versus temperature T of  SrMn2P2 and CaMn2P2 crystals.  The vertical spikes at the antiferromagnetic ordering temperatures demonstrate a weak first-order transition in SrMn2P2 and a strong one in CaMn2P2
Significance and Impact

First-order antiferromagnetic transitions are extremely rare. Magnetic transitions and the associated role of magnetic frustrations are key to developing novel magnetic materials of technological importance.

Research Details
  • Synchrotron x-ray diffraction measurements of both compounds showed that the first-order transitions are not associated with crystal-structure changes but rather with the antiferromagnetic transitions.
  • The first-order transitions are observed in heat capacity, magnetic susceptibility and nuclear magnetic resonance measurements.

N. S. Sangeetha, S. Pakhira, Q.-P. Ding, L. Krause, H.-C. Lee, V. Smetana, A.-V. Mudring, B. Brummerstedt Iversen, Y. Furukawa, and D. C. Johnston, "First-order antiferromagnetic transitions of SrMn2P2and CaMn2P2single crystals containingcorrugated-honeycomb Mn sublattices," PNAS 2021 Vol. 118 No. 44 e2108724118.