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arXiv · 0901.1749

Magnetic and dielectric properties of A2CoSi2O7 (A=Ca, Sr, Ba) crystals

M. Akaki·J. Tozawa·D. Akahoshi·H. Kuwahara
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Abstract

We have investigated the magnetic and dielectric properties of $A_2$CoSi$_2$O$_7$ ($A$=Ca, Sr, and Ba) crystals with a two-dimensional network of CoO$_4$ and SiO$_4$ tetrahedra connected with each other through the corners. In Ca$_2$CoSi$_2$O$_7$, a weak ferromagnetic transition occurs at 5.7 K, where the dielectric constant parallel to the c axis shows a concomitant anomaly. The large magnetocapacitance effect is observed below 5.7 K; $Δ\varepsilon (H)/\varepsilon (0) \equiv [\varepsilon (H)-\varepsilon (0)]/\varepsilon (0)$ reaches 13 % at 5.1 K\@. These results indicate a strong coupling between the magnetism and dielectricity in Ca$_2$CoSi$_2$O$_7$. Sr$_2$CoSi$_2$O$_7$ shows a similar magnetoelectric behavior to that of Ca$_2$CoSi$_2$O$_7$. In contrast, in Ba$_2$CoSi$_2$O$_7$, which has the different arrangement of SiO$_4$ and CoO$_4$ tetrahedra from that of Ca$_2$CoSi$_2$O$_7$, the magnetocapacitance is hardly observed. The key for the magnetocapacitance effect of $A_2$CoSi$_2$O$_7$ lies in the quasi-two-dimensional crystal structure.

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M. Akaki, J. Tozawa, D. Akahoshi, H. Kuwahara. 2009-01-13. Magnetic and dielectric properties of A2CoSi2O7 (A=Ca, Sr, Ba) crystals. https://doi.org/10.1088/1742-6596/150/4/042001

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