# Structural and magnetic properties of spin-$1/2$ dimer compound Cu$_2$(IPA)$_2$(DMF)(H$_2$O) with a large spin gap

## TL;DR

This study synthesizes and characterizes a copper-based organic compound with a large spin gap, revealing its structural details and magnetic behavior consistent with a spin-1/2 dimer model, and confirms the absence of magnetic order at low temperatures.

## Contribution

The paper provides a comprehensive structural and magnetic analysis of a new copper-organic compound with a large spin gap, including synthesis, crystallography, and magnetic measurements, highlighting its potential as a spin-dimer system.

## Key findings

- Large spin gap of approximately 409 K confirmed.
- No magnetic long-range order observed down to 2 K.
- Structural analysis reveals spin dimers formed by Cu$^{2+}$ ions in a layered arrangement.

## Abstract

We present the synthesis and a detailed investigation of structural and magnetic properties of metal-organic compound Cu$_2$(IPA)$_2$(DMF)(H$_2$O) by means of x-ray diffraction, magnetization, and heat capacity measurements. Single crystals of the title compound were synthesized by judicious selection of organic ligand and employing a selective hydrothermal reaction route. It crystallizes in an orthorhombic structure with space group $Cmca$. The structural analysis revealed that two Cu$^{2+}$ ions are held together by the organic component (-O-C-O-) in a square paddle-wheel to form spin dimers which are aligned perpendicular to each other and are further coupled through organic ligands (isophthalic acid) forming two-dimensional layers. Temperature dependent magnetic susceptibility $\chi(T)$ could be described well using spin-$1/2$ dimer model. The spin susceptibility $\chi_{\rm spin} (T)$ shows an exponential decrease in the low temperature region, below the broad maximum, confirming the singlet ground state with a large spin gap of $\Delta/k_{\rm B} \simeq 409$~K. The heat capacity $C_{\rm p}$ measured as a function of temperature also confirms the absence of magnetic long-range-order down to 2~K.