Multiferroics exhibit more than one primary ferroic ordering, including ferromagnetism, ferroelectricity, or ferroelasticity in the same phase^[1,2]. The terminology is usually extended to include non-primary orderings such as antiferromagnetism, antiferroelectricity, as well as composites of individual ferroics. The concept often used today is referred to magnetoelectric materiasl combing ferroelectric and magnetic behaviors (Fig. 1);. Such a combination of ferroic orders in multiferroics can lead to coupling between them and provide an efficient route to control magnetism by electric fields or vice versa.

Multiferroics can be classified into two categories: type-I mulitferroics refer to the ferroelectricity does not have magnetic origin, which usually leads to an indirect and weak magnetoelectric coupling; Type-II multiferroics are induced by some specific magnetic orders with a strong magnetoelectric coupling but a small electric polarization and thus low transition temperature (T_C). The two types are depicted in Fig. 2^[3]

In geometrically driven ferroelectrics, a small A-site cation permits rotations of its surrounding coordination polyhedral (Fig. 3b), which are either polar in their own right (for example, in BaNiF4^[6]) or couple to a secondary polar distortion (as in YMnO3^[7]). In this case, the polarization is both robust and small in magnitude. In h-RMnO3 (R=Sc, Y, In or Dy-Lu^[8,9]), unit-cell tripling drives the emergence of a ferroelectric order at Tc ≥ 1,200 K with a polarization of 5.6 μC/cm2, followed by a magnetic ordering at the Neel temperature (TN ≤ 120 K).

In magnetically induced ferroelectrics, a non-collinear magnetic ordering, such as a spin spiral, breaks the inversion symmetry and induces a spontaneous polarization. These magnetically induced, so-called improper ferroelectric materials are totally different from displacive ferroelectrics, in which magnetic ordering is inhibited. The most intensely discussed mechanism is the inverse Dzyaloshinskii–Moriya (DM) interaction. Spin-orbit coupling (SOC) is crucial for the inverse DM interaction. The polarization is essentially determined by the optimization of the spin configuration from the point of view of anitsymmetry exchange, expressed by the antisymmetric product S_i × S_j of neighboring spins Si,j (see Fig. 3d). The polarization vector is P ∝ e_ij × ( S_i × S_j), where eij is the unit vector connecting neighboring spins. Multiferroicity of this type was first found in Cr2BeO4^[11].

When electrons pass through atomically thin 2D materials, energy can be either elastically or inelastically transferred to the targeted atom. During an elastic collision, impinging electrons are scattered to high angles by the recoiling nucleus and energy and momentum are both conserved. During the inelastic scattering process, the incident electron interacts with the electronic system of the target atom resulting in electronic excitation and electrostatic charging ^[1]

Atomic clusters, consisting of a few to a few thousand atoms, have emerged over the past 40 years as the ultimate nanoparticles. Some of these clusters form stable units with atomically precise structures that give rise to collective behaviors that mimic those of traditional atoms, essentially functioning as ‘superatoms’^{[1, 2]}. The ultimate vision is to create materials with tailored and tuneable functions through the judicious design, synthesis and assembly of superatoms. The use of superatoms as building blocks for materials offers opportunities to design materials with tailored functionalities^{[3, 4]}.

However, the reinforcing chemical interaction between atoms (chemical bond)^{[5, 6]}is the main factor that leads to the unstable structure of atomic crystal through the replacement of elements, and the weakening of such interaction is likely to overcome this difficulty. In the superatomic crystal materials with atomic clusters as the basic building unit, the surface saturated atomic clusters can be combined by non-covalent interactions such as weak atom identification, electrostatic interaction^[7] and hydrogen bonding^[8]. It has the potential to maintain structural stability in the regulation of electronic structural properties through continuous cluster (element) replacement, and is also more in line with the needs of large-scale material preparation, with some characteristics of atomic fabrication.