Magnetic and dielectric properties of quasi-two-dimensional manganese oxide Sr7Mn4O15

Using dc magnetic susceptibility, electron spin resonance (ESR) and dielectric spectroscopy techniques, we investigate the magnetic and dielectric properties of Sr7Mn4O15, which has a layered structure with pairs of face-sharing octahedra Mn2O9. Magnetic susceptibility reveals the Néel temperature TN∼70.5 K, above which Sr7Mn4O15 manifests intense short range order. ESR spectra indicate the existence of a transition at about 370 K, confirming the suggested spin pairing in the Mn2O9 units. In the dielectric spectra, a sudden drop of permittivity is observed at TN, revealing the existence of strong spin–lattice coupling in Sr7Mn4O15.

► Sr7Mn4O15 was synthesized through organic polymeric gel route.
► Direct evidence for the Mn spin pairing in Mn2O9 units was obtained from ESR analysis.
► Dielectric spectra revealed Sr7Mn4O15 to be a system with strong spin–lattice coupling.