Multifunctionality of Layered Materials

Layered materials have attracted a lot of attention due to their multifunctionality. We use the term “layered materials” to describe compounds with relatively strong chemical bonding in two dimensions (in-plane) compared to much weaker interactions in the out-of-plane direction due to interlayer distances that are much larger than typical interatomic spacings. We concentrate on the unique thermal, electrical and magnetic properties that arise from their two-dimensional connectivity. We divide the compounds into two categories. The first category includes the family of all-inorganic IV-VI semiconductors. We investigate the emerging family of Ge-chalcogenides with their rich polymorphism that can be obtained by alloying. The change in crystal structure influences the electronic band structure, which affects electrical transport properties significantly and increases the thermoelectric performance. The second category of layered compounds comprises two-dimensional organic-inorganic perovskites. We focus on their rich structural and magnetic properties. The structures of layered hybrid perovskites are flexible and compatible with a wide range of both inorganic and organic components, which together dictate the physical properties that they possess and lead to a large variety of different structures and properties. We pay particular attention to investigating the magnetic properties of layered organic-inorganic perovskites. This thesis shows that layered materials possess many functionalities for which the structure and physical properties are highly correlated. By studying only a few selected layered materials, we demonstrate that this research area is vast, and that many unique properties can be found only in materials with two-dimensional chemical connectivit

Magnetocaloric effect and critical behavior in arylamine-based copper chloride layered organic-inorganic perovskite

Layered organic-inorganic hybrid perovskites have been the focus of much research regarding their optoelectronic and multiferroic properties. Here, we demonstrate the presence of a large magnetocaloric effect in the ferromagnetic layered perovskite phenylmethylammonium copper chloride ((PMA)2CuCl4) below the Curie temperature of ∼9.5 K. We measure a magnetic entropy change ranging from 0.88 J/kg.K to 2.98 J/kg.K in applied fields of 10 kOe and 70 kOe, respectively. We also study the nature of the magnetic phase transition using critical isotherm analysis. The critical exponents are consistent with the 2D-XY spin model

Polar Structure and Two-Dimensional Heisenberg Antiferromagnetic Properties of Arylamine-Based Manganese Chloride Layered Organic-Inorganic Perovskites

The breaking of inversion symmetry can enhance the multifunctional properties of layered hybrid organic-inorganic perovskites. However, the mechanisms by which inversion symmetry can be broken are not well-understood. Here, we study a series of MnCl4-based 2D perovskites with arylamine cations, namely, (C6H5CxH2xNH3)2MnCl4 (x = 0, 1, 2, 3), for which the x = 0, 1, and 3 members are reported for the first time. The compounds with x = 1, 2, and 3 adopt polar crystal structures to well above room temperature. We argue that the inversion symmetry breaking in these compounds is related to the rotational degree of freedom of the organic cations, which determine the hydrogen bonding pattern that links the organic and inorganic layers. We show that the tilting of MnCl6 octahedra is not the primary mechanism involved in inversion symmetry breaking in these materials. All four compounds show 2D Heisenberg antiferromagnetic behavior. A ferromagnetic component develops in each case below the long-range magnetic ordering temperature of μ42-46 K due to spin canting

CCDC 2074097: Experimental Crystal Structure Determination

Related Article: Liany Septiany, Diana Tulip, Mikhail Chislov, Jacob Baas, Graeme R. Blake|2021|Inorg.Chem.|60|15151|doi:10.1021/acs.inorgchem.1c0101

CCDC 2074098: Experimental Crystal Structure Determination

Related Article: Liany Septiany, Diana Tulip, Mikhail Chislov, Jacob Baas, Graeme R. Blake|2021|Inorg.Chem.|60|15151|doi:10.1021/acs.inorgchem.1c0101

CCDC 2074096: Experimental Crystal Structure Determination

Related Article: Liany Septiany, Diana Tulip, Mikhail Chislov, Jacob Baas, Graeme R. Blake|2021|Inorg.Chem.|60|15151|doi:10.1021/acs.inorgchem.1c0101