Synthesis and magnetic properties of spin-$\frac{3}{2}$ $\gamma$-phase of SrCo$_{2}$(PO$_{4}$)$_{2}$ antiferromagnet

TL;DR

This study synthesizes a new gamma-phase of SrCo₂(PO₄)₂ with spin-3/2, revealing its triclinic structure, antiferromagnetic order below 8.5 K, and field-induced magnetic transitions through comprehensive magnetic and thermodynamic measurements.

Contribution

The paper reports the first synthesis and detailed characterization of the gamma-phase of SrCo₂(PO₄)₂, including its structure, magnetic properties, and field-induced phenomena, which were previously unexplored.

Findings

Antiferromagnetic order below 8.5 K

Field-induced spin-flop transition at ~4.5 Tesla

Magnetic-field-induced transitions at 3.6 K and 7.4 K

Abstract

We report on the synthesis of a new $\gamma$-phase of the spin $S$~=~$\frac{3}{2}$ compound SrCo$_2$(PO$_4$)$_2$ together with a detailed structural, magnetic and thermodynamic properties. The $\gamma$-phase of SrCo$_2$(PO$_4$)$_2$ crystallizes in a triclinic crystal structure with the space group $P\bar{1}$. Susceptibility and specific heat measurements reveal that SrCo$_2$(PO$_4$)$_2$ orders antiferromagnetically below $T_{\rm N}\simeq 8.5$\,K and the nature of ordering is three dimensional (3D). The magnetic isotherm at temperatures below $T_{\rm N}$ shows a field-induced spin-flop transition, related to the magnetocrystalline anisotropy, at an applied field of $\sim$~4.5~Tesla. Remarkably, heat capacity shows magnetic-field-induced transitions at $T_{\rm N1}$ = 3.6 K and $T_{\rm N2}$ = 7.4 K. The magnetic long range ordering (LRO) is also confirmed in both the Knight shift and spin-lattice relaxation rate ($1/T_{1}$) of the $^{31}$P-NMR measurements. However, below the LRO we have not detected any NMR signal due to faster relaxation. We have detected two structurally different phosphorous sites in $\gamma$-phase of SrCo$_{2}$(PO$_{4}$)$_{2}$ and they shift differently with temperature.