Magnetoelectric Properties of (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$ Crystals

TL;DR

This study explores how substituting Sr for Ca in (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$ crystals affects their magnetoelectric properties, revealing changes in magnetic transition temperature, dielectric response, and magnetocapacitance effects.

Contribution

It provides new insights into the influence of Sr substitution on the magnetoelectric coupling and dielectric properties of (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$ crystals.

Findings

Magnetic transition temperature increases with Sr content.

Positive magnetocapacitance diminishes and disappears for $x extgreater=0.5$.

Negative magnetocapacitance is enhanced by Sr substitution.

Abstract

We have investigated the magnetoelectric properties of (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$ ($0\leq x\leq 1$) crystals with a quasi-two-dimensional structure. In Ca$_2$CoSi$_2$O$_7$ ($x=0$), a canted antiferromagnetic transition occurs at 5.6 K. The transition temperature $T_{\rm N}$ is increasing with increasing Sr concentration, and the rises of the magnetization and dielectric constant become larger. Since the dielectric constant shows large change at $T_{\rm N}$ and the magnetocapacitance effect is observed below $T_{\rm N}$, a coupling between the magnetism and dielectricity is strong in (Ca$_{1-x}$Sr$_{x}$)$_2$CoSi$_2$O$_7$. The positive magnetocapacitance is reduced by Sr substitution, and is not observed in $x\geq 0.5$. Namely, the compound of $x\geq 0.5$ does not show the magnetic-field-induced electric polarization. On the other hand, the negative magnetocapacitance is enhanced by Sr substitution.