Study on Paramagnetic Interactions of (CH(3)NH(3))(2)CoBr(4) Hybrid Perovskites Based on Nuclear Magnetic Resonance (NMR) Relaxation Time

The thermal properties of organic–inorganic (CH(3)NH(3))(2)CoBr(4) crystals were investigated using differential scanning calorimetry and thermogravimetric analysis. The phase transition and partial decomposition temperatures were observed at 460 K and 572 K. Nuclear magnetic resonance (NMR) chemical shifts depend on the local field at the site of the resonating nucleus. In addition, temperature-dependent spin–lattice relaxation times (T(1ρ)) were measured using (1)H and (13)C magic angle spinning NMR to elucidate the paramagnetic interactions of the (CH(3)NH(3))(+) cations. The shortening of (1)H and (13)C T(1ρ) of the (CH(3)NH(3))(2)CoBr(4) crystals are due to the paramagnetic Co(2+) effect. Moreover, the physical properties of (CH(3)NH(3))(2)CoBr(4) with paramagnetic ions and those of (CH(3)NH(3))(2)CdBr(4) without paramagnetic ions are reported and compared.