First order transition in trigonal structure ${\textbf{Ca}}{\textbf{Mn}}_{2}{\textbf{P}}_{2}$

Y. J. Li; F. Jin; Z. Y. Mi; J. Guo; W. Wu; D. S. Wu; S. H. Na; C. Mu; X. B. Zhou; Z. Li; K. Liu; L. L. Sun; Q. M. Zhang; T. Xiang; G. Li; J. L. Luo

doi:10.1209/0295-5075/132/46001

paper

First order transition in trigonal structure $Ca Mn_{2} P_{2}$

arXiv:2012.01863 · doi:10.1209/0295-5075/132/46001

Abstract

We report structural and physical properties of the single crystalline $Ca Mn_{2} P_{2}$ . The X-ray diffraction(XRD) results show that $Ca Mn_{2} P_{2}$ adopts the trigonal $Ca Al_{2} Si_{2}$ -type structure. Temperature dependent electrical resistivity $ρ (T)$ measurements indicate an insulating ground state for $Ca Mn_{2} P_{2}$ with activation energies of 40 meV and 0.64 meV for two distinct regions, respectively. Magnetization measurements show no apparent magnetic phase transition under 400 K. Different from other $A Mn_{2} Pn_{2}$ (A = Ca, Sr, and Ba, and Pn = P, As, and Sb) compounds with the same structure, heat capacity $C_{p} (T)$ and $ρ (T)$ reveal that $Ca Mn_{2} P_{2}$ has a first-order transition at $T$ = 69.5 K and the transition temperature shifts to high temperature upon increasing pressure. The emergence of plenty of new Raman modes below the transition, clearly suggests a change in symmetry accompanying the transition. The combination of the structural, transport, thermal and magnetic measurements, points to an unusual origin of the transition.

6 pages, 6 figures. Accepted by Europhysics Letters

First order transition in trigonal structure CaMn2​P2​

Abstract

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First order transition in trigonal structure $Ca Mn_{2} P_{2}$