Field-induced spin-structural transition and giant magnetostriction in Ising chain $\alpha$-CoV$_2$O$_6$

TL;DR

This study reveals a field-induced spin-structural transition and giant magnetostriction in $ ext{α-CoV}_2 ext{O}_6$, highlighting strong spin-lattice coupling and complex magnetic behavior in this quasi-one-dimensional Ising chain compound.

Contribution

It provides the first detailed investigation of the magnetic, thermal, and structural responses of $ ext{α-CoV}_2 ext{O}_6$ under magnetic fields, demonstrating a giant magnetostriction linked to spin-structural transitions.

Findings

Effective $S=1/2$ Ising state below 20 K.

Large positive magnetostriction up to 9 T.

Field-induced first order magnetic transitions.

Abstract

We have investigated the temperature and magnetic field dependence of magnetization, specific heat ($C_p$), and relative sample length change ($\Delta L/L_0$) for understanding the field-induced spin-structural change in quasi-one-dimensional spin chain $\alpha$-CoV$_2$O$_6$ which undergoes antiferromagnetic (AFM) transition below $T_N$$=$15 K. Analysis of $C_p$($T$) shows that an effective $S$$=$1/2 Ising state is realized below 20 K, though the magnetic fluctuations persist well above $T_N$. $C_p$ and the coefficient of linear thermal expansion ($\alpha$) exhibit strong $H$ dependence in the AFM state. We also observe a huge positive magnetostriction [$\Delta L$($H$)/$L_0$] below 20 K which does not show any tendency of saturation up to 9 T. With increasing field, a sharp and symmetric peak emerges below $T_N$ in both $C_p$($T$) and $\alpha$($T$) due to field-induced first order ferrimagnetic/ferromagnetic-paramagnetic transitions. The large value of magnetostriction below $T_N$ suggests strong spin-lattice coupling in $\alpha$-CoV$_2$O$_6$.