Transition Metal Adsorbed-Doped ZnO Monolayer: 2D Dilute Magnetic Semiconductor, Magnetic Mechanism, and Beyond 2D

Abstract

As an improvement over organic or inorganic layered crystals, the synthetic monolayer ZnO(M) inherits semiconductivity and hostability from its bulk, yet it acts as a promising host for dilute magnetic semiconductors. Here, we report the electronic and magnetic properties of ZnO(M) doped with one 3d transition metal ion and simultaneously adsorbed with another 3d transition metal ion. Two sequences are studied, one where the dopant is fixed to Mn and the adsorbate is varied from Sc to Zn and another where the dopant and adsorbate are reversed. First-principles results show that the stable adsorbed−doped systems possess a lower bandgap energy than that of the host. System magnetic moments can be tuned to |5 – x |μ B , where x refers to the magnetic moment of the individual 3d atom. An interplay between superexchange and direct exchange yields a ferromagnetic system dually adsorbed−doped with Mn. In addition to a novel material design route, the magnetic interaction mechanism is found beyond two dimensions, having been identified for its three-dimensional bulk and zero-dimensional cluster counterparts.

Introducing Magnetism into 2D Nonmagnetic Inorganic Layered Crystals: A Brief Review from First-Principles Aspects

“…The interplay between superexchange and direct exchange is shown in Figure 7e. As seen in the Mn-doped-adsorbed mZnO, the interplay between the magnetic superexchange and direct exchange enables AFM in the system [82]. A similar observation was found in the Fe dually doped MoS2 mono-and multilayers.…”

“…In a recent study, Zhang et al showed that, after substituting the Zn to a 3d TM, the host monolayer was still able to adsorb another TM atom. The system magnetic moments follow the formula of |5 − x| µB, where x refers to the MM of the individual 3d atom [82].…”

“…Both d orbitals from the adsorbed and doped Mn atoms coincide with the p orbital from the same O atom, which is visualized as the sharp peaks in Figure 4c. An interplay between magnetic superexchange (ion-matrix-ion) and direct exchange (ion-ion) is identified, which renders the complex AFM [82]. Dimensionality reduction, by reducing the spatial variables, introduces spatial symmetry effects into the doped ILC systems.…”

Orienting spins in dually doped monolayer MoS2: from one-sided to double-sided doping

“…The spin interactions of doubly-doped ILC systems are beyond explanations furnished by conventional interpretations of magnetic mechanisms in DMS systems. 41 Magnetic exchange schemes or their interplays 42 are not valid here due to distances or absence of a nonmetal atom between the dopants. Magnetic interactions through the electron sea of the host are vetoed in present semiconducting systems, invalidating explanations from Kondo effect.…”

Density functional theory study on the effect of Cu- and Na-substituted layers on spin-dependent transport and TMR in the Fe/ZnO/Fe MTJ

“…The crystal structures shared by zinc oxide (ZnO) are wurtzite hexagonal, zinc blend, and rock salt [9]. It is accepted that pure ZnO is a non-magnetic material [10,11]. In the past decade, novel functionalities of ZnO with wurtzite crystalline structure in the electronic, optoelectronic, and spintronic applications have been extensively studied, theoretically and experimentally [12][13][14][15][16].…”