First-order antiferromagnetic transitions of SrMn <sub>2</sub> P <sub>2</sub> and CaMn <sub>2</sub> P <sub>2</sub> single crystals containing corrugated-honeycomb Mn sublattices
N. S. Sangeetha, Santanu Pakhira, Qing-Ping Ding, Lennard Krause, Hyung-Cheol Lee, Volodymyr Smetana, Anja-Verena Mudring, Bo Brummerstedt Iversen, Yuji Furukawa, David C. Johnston
Abstract
Significance With rare exceptions, an antiferromagnetic (AFM) transition in zero magnetic field is thermodynamically of second order where the thermal-average magnetic moments of the magnetic atoms (ordered moments) vary continuously on cooling through the AFM ordering temperature <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mtext>N</mml:mtext> </mml:msub> </mml:mrow> </mml:math> with no latent heat at the transition. Such materials include the AFM pnictides CaMn 2 As 2 , SrMn 2 As 2 , CaMn 2 Sb 2 , SrMn 2 Sb 2 , and CaMn 2 Bi 2 . Here we demonstrate that the closely related SrMn 2 P 2 and CaMn 2 P 2 insulators instead exhibit first-order AFM transitions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mtext>N</mml:mtext> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>53</mml:mn> </mml:mrow> </mml:math> and 70 K, respectively, where the heat capacity exhibits a latent heat at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mtext>N</mml:mtext> </mml:msub> </mml:mrow> </mml:math> . The mechanism causing these first-order transitions remains to be explained, but its understanding may lead to the development of novel magnetic materials of technological interest.