Coupling of the Structure and Magnetism to Spin Splitting in Hybrid Organic–Inorganic Perovskites

Abstract

Hybrid organic−inorganic perovskites are famous for the diversity of their chemical compositions, phases, phase transitions, and associated physical properties. We use a combination of experimental and computational techniques to reveal a strong coupling between structure, magnetism, and spin splitting in a representative of the largest family of hybrid organic−inorganic perovskites: the formates. With the help of first-principles simulations, we find spin splitting in both conduction and valence bands of [NH 2 NH 3 ]Co(HCOO) 3 induced by spin−orbit interactions, which can reach up to 14 meV. Our magnetic measurements reveal that this material exhibits canted antiferromagnetism below 15.5 K. The direction of the associated antiferromagnetic order parameter is strongly coupled with spin splitting in the centrosymmetric phase, allowing for the creation and annihilation of spin splitting through the application of a magnetic field. Furthermore, the structural phase transition to the experimentally observed polar Pna2 1 phase completely changes the aforementioned spin splitting and its coupling to magnetic degrees of freedom. This reveals that in [NH 2 NH 3 ]Co(HCOO) 3 , the structure and magnetism are strongly coupled to spin splitting and can be manipulated through electric and magnetic fields. We believe that our findings offer an important step toward a fundamental understanding and practical applications of materials with coupled properties.

Experimental Observation of the Fully Ferroelectric–Fully Ferroelastic Effect in Multiferroic Hybrid Perovskites

“…Multiferroic was initially coined by Aizu in 1968 with the theoretical identification of 42 species of simultaneously ferroelectric and ferroelastic phase transition . The famous inorganic Gd 2 (MoO 4 ) 3 with the fully ferroelectric–fully ferroelastic effect was predicted and successfully validated in 1968, serving as a typical model for fully multiferroic over subsequent decades. , The characteristic of a type of ferroelectric–ferroelastic crystal is that the concurrent alteration of the polarization vector alongside changes in the strain tensor, and vice versa, is fully ferroelectric and fully ferroelastic. − Capitalizing on these dual ferroic effects, the development of high-precision electronic micropositioners, tunable radio frequency filters, compatible grating devices, and adaptive devices has become feasible. − Furthermore, the synergy between ferroelectricity and ferroelasticity can markedly enhance material physical properties. , For example, You et al reported a hybrid perovskite multiferroic [Me 3 NCH 2 Cl]­CdCl 3 , whose illustrious electromechanical conversion performance has been proven to be closely related to the partial coupling of ferroelectricity and ferroelasticity. , Benefiting from the numerous advantages of intimate interplay between full ferroelectricity and full ferroelasticity, recently, a large amount of studies have focused on exploring multiferroic materials with ferroelectricity and ferroelasticity. − However, constructing ferroelectric that is compatible with ferroelasticity has been a great challenge due to the strict requirements of crystallographic symmetry, reasonable symmetry breaking, and ingenious evolution of lattice parameters. − …”