Magnetodielectric coupling and multi-blocking effect in the Ising-chain magnet Sr 2 Ca 2 CoMn 2 O 9

• Published in: Journal of applied physics 2021-07, Vol.130 (3)
• Main Authors: Basu, T., Sakly, N., Pautrat, A., Veillon, F., Pérez, O., Caignaert, V., Raveau, B., Hardy, V.
• Format: Article
• Language: English
• Subjects: Condensed Matter; Materials Science; Physics
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0056149

We have demonstrated magnetodielectric (MD) coupling in an Ising-chain magnet Sr 2 Ca 2 CoMn 2 O 9 via detailed investigation of ac susceptibility and dielectric constant as a function of temperature, magnetic field, and frequency. Sr 2 Ca 2 CoMn 2 O 9 consists of spin-chains made of the regular stacking of one CoO 6 trigonal prism with two MnO 6 octahedra. The (Co 2+-Mn 4+-Mn 4+) unit stabilizes a (↑↓↑) spin-state along the chains that are distributed on a triangular lattice. This compound undergoes a partially disordered antiferromagnetic transition at T N ∼ 28 K. The dielectric constant exhibits a clear peak at T N only in the presence of an external magnetic field (H ≥ 5 kOe), evidencing the presence of MD coupling, which is further confirmed by field-dependent dielectric measurements. We argue that spatial inversion symmetry can be broken as a result of exchange-striction along each spin chain, inducing uncompensated local dipoles. At low temperatures, a dipolar relaxation phenomenon is observed, bearing strong similarities to the blocking effect typical of spin dynamics in this compound. Such a spin-dipole relationship is referred to as a "multiblocking" effect, in relation to the concept of magnetodielectric "multiglass" previously introduced for related materials.