Magnetic correlations of the quasi-one-dimensional half-integer spin-chain antiferromagnets Sr$M_2$V$_2$O$_8$ ($M$ = Co, Mn)

TL;DR

This study investigates magnetic correlations in quasi-one-dimensional Sr$M_2$V$_2$O$_8$ compounds with M=Co, Mn, revealing distinct antiferromagnetic structures, universality classes, and quantum fluctuations through neutron diffraction and magnetization analysis.

Contribution

It provides the first detailed comparison of magnetic structures and critical behavior in Sr$M_2$V$_2$O$_8$ compounds with different magnetic ions, highlighting their universality classes and quantum effects.

Findings

Different AFM structures below 5.2 K and 42.2 K for Co and Mn compounds.

Mn-compound exhibits ferromagnetic chains in the ab plane; Co-compound shows mixed AFM/F ordering.

Both compounds show quantum fluctuations indicated by reduced ordered moments.

Abstract

Magnetic correlations of two iso-structural quasi-one-dimensional (1D) antiferromagnetic spin-chain compounds Sr$M_2$V$_2$O$_8$ ($M$ = Co, Mn) have been investigated by magnetization and powder neutron diffraction. Two different collinear antiferromagnetic (AFM) structures, characterized by the propagation vectors, $k$ = (0 0 1) and $k$ = (0 0 0), have been found below $\sim$ 5.2 K and $\sim$ 42.2 K for the Co- and Mn-compounds, respectively. For the Mn-compound, AFM chains (along the $c$ axis) order ferromagnetically within the $ab$ plane, whereas, for the Co-compound, AFM chains order ferro-/antiferromagnetically along the $a/b$ direction. The critical exponent study confirms that the Co- and Mn-compounds belong to the Ising and Heisenberg universality classes, respectively. For both compounds, short-range spin-spin correlations are present over a wide temperature range above $T_N$. The reduced ordered moments at base temperature (1.5 K) indicate the presence of quantum fluctuations in both compounds due to the quasi-1D magnetic interactions.