Interlayer coupling in EuS/SrS, EuS/PbSe and EuS/PbTe magnetic semiconductor superlattices

Abstract

Neutron reflectivity studies of EuS/SrS, EuS/PbSe and EuS/PbTe all-semiconductor superlattices were carried out in a search for exchange interlayer coupling. A relatively weak antiferromagnetic coupling was found in EuS/SrS and EuS/PbSe systems but no interlayer coupling was detected in EuS/PbTe superlattices. In EuS/SrS, where the SrS spacer is an insulator (E(g)≈4 eV), a very weak and short range interlayer coupling is in agreement with the earlier theoretical predictions that the interlayer coupling strength in EuS-based magnetic semiconductor superlattices depends strongly on the energy gap of the nonmagnetic layer and should decrease with an increase of the energy gap of the spacer material. A weak coupling in EuS/PbSe and no coupling in EuS/PbTe, where both PbSe and PbTe are narrow-gap semiconductors (E(g)≈0.3 eV), is in disagreement not only with the theoretical expectations but also in stark contrast with earlier results for another narrow-gap spacer system, EuS/PbS, where pronounced antiferromagnetic coupling persists even in samples with PbS layer thicknesses as large as 200 Å. A possible influence of the increasing lattice mismatch between EuS and the spacer materials (0.5%, 0.8%, 2.5% and 8.2% for PbS, SrS, PbSe and PbTe, respectively) on the magnetic ordering of the EuS layer near the interfaces and, consequently, on the interlayer coupling is discussed.

A two-dimensional α-As/α-AsP van der Waals heterostructure for photovoltaic applications

“…An analogous puckered shape and a tiny lattice mismatch assured the feasibility of the proposed 2D α-As/α-AsP vdWH. In the heterostructure, previous experimental 47–49 and theoretical 50–52 studies have proved that a lattice mismatch less than 10% was acceptable. Therefore, we construct the 2D α-As/α-AsP vdWH by stacking 2D α-AsP on 2D α-As.…”

Inducing magnetism onto the surface of a topological crystalline insulator

“…Figure 1(a) illustrates the SnTe (14nm) / EuS (3nm) / SnTe (10nm) trilayer structure grown on Si (100). 32,33,34 SnTe 35 and EuS were both grown by e-beam evaporation from composite sources (see supplement S1 for details). [36][37][38][39][40][41] The structure of the trilayer was studied by X-ray diffraction and crosssectional transmission electron microscopy (XTEM).…”

Divalent Europium Nanocrystals: Controllable Synthesis, Properties, and Applications

“…The substitution of the Eu 2 + ions with La 3 + ions, whose ionic radius is smaller than that of Eu 2 + ions, is effective for both lattice contraction and charge doping. [85] Single-crystalline La-doped EuO thin films were grown by using the molecular beam epitaxy (MBE) method. [86] The La-doped EuO thin films had a T C up to 200 K. The similar lattice parameters of the same rock-salt structure types (5.968 for EuS as compared to 5.5655 for GdS) and similar ionic radii (1.15 for Eu 2 + as compared to 1.12 for Gd 2 + and 0.938 for Gd 3 + ) allow for exchange of Eu ions with Gd ions to create doped crystals for all ratios of Eu and Gd.…”