Magnetic Binary Silicide Nanostructures

Abstract

In spite of numerous advantageous properties of silicides, magnetic properties are not among them. Here, the magnetic properties of epitaxial binary silicide nanostructures are discussed. The vast majority of binary transition-metal silicides lack ferromagnetic order in their bulk-size crystals. Silicides based on rare-earth metals are usually weak ferromagnets or antiferromagnets, yet both groups tend to exhibit increased magnetic ordering in low-dimensional nanostructures, in particular at low temperatures. The origin of this surprising phenomenon lies in undercoordinated atoms at the nanostructure extremities, such as 2D (surfaces/interfaces), 1D (edges), and 0D (corners) boundaries. Uncompensated superspins of edge atoms increase the nanostructure magnetic shape anisotropy to the extent where it prevails over its magnetocrystalline counterpart, thus providing a plausible route toward the design of a magnetic response from nanostructure arrays in Si-based devices, such as bit-patterned magnetic recording media and spin injectors.

Lattice-Match Stabilization and Magnetic Properties of Metastable Epitaxial Permalloy-Disilicide Nanostructures on a Vicinal Si(111) Substrate

“…In densely packed arrays, interparticle interaction via dipolar fields may take place, leading to superspin glass (SSG) or superferromagnetic (SFM) state, [ 13 , 14 , 15 ]. These three phenomena of “Supermagnetism” (SPM, SSG and SFM), were previously reported by us to take place in epitaxially self-assembled silicide NSs of transition and rare-earth metals, of nonferromagnetic bulk phase origins [ 16 , 17 , 18 , 19 , 20 , 21 ]. Often, at least one-dimensional (1D) in-plane ordering of self-assembled silicide phase NSs can be achieved by their decoration of the periodic vicinal Si(hkl) surface step bunches [ 22 , 23 ], as shown in Figure 1 for 5°-miscut Si(111) in this work.…”

“…While defect-induced supermagnetism can be considered “extrinsic”, composition, crystal structure, and the resulting electronic structure of binary (or higher) compounds may still have a sizeable “intrinsic” effect on the overall magnetic properties of compound NSs [ 21 ]. Metal silicides usually exhibit a sequence of equilibrium phases and epitaxially-stabilized metastable structures.…”

“…Depending on deposition method, coverage and heat treatment for Fe−Si reaction, multiple silicide phases and their metastable variants viz. α , β , γ , s , have been reported, with miscellaneous structural and physical properties [ 21 ]. α- phase crystallizes in a tetragonal structure and is metallic, whereas the β -phase has an orthorhombic crystal structure and is semiconducting with a direct 0.87 eV band gap, suitable for application in optical fiber communication, thermoelectricity and optoelectronics.…”

Interface Effects on Epilayer Surface Density of States by Scanning Tunneling Spectroscopy and Density Functional Theory

“…refs. []). In UHV (base pressure 1 × 10 −8 Pa), after thorough degassing, the native silicon oxide was evaporated by repeated flashes at 1150–1200 °C, and the clean Si surface was slowly cooled until well‐ordered (7 × 7) reconstruction appeared in diffraction and STM (pristine surface similar to that in ref.…”

“…Though mostly employed as a contact material in electronic devices, recent studies of mesoscopic and nanometric nickel silicide structures have shed light on their other less known properties. Nanoscale Ni 2 Si, for example, has been suggested to display unexpected magnetic properties . Characterization of nano‐structures in general has been the focus of numerous studies, and a plethora of techniques and methods have been for this purpose.…”