Spin reorientation transitions and structures of electrodeposited Ni/Cu(100) ultrathin films with and without Pb additives

Abstract

Magnetic properties and surface structures of Ni/Cu(100) ultrathin films are studied by means of magneto-optical Kerr effect and in situ scanning tunneling microscopy in combination with cyclic voltammetry. At the initial stage of Ni deposition on a Cu(100) electrode, nickel atoms attach onto the steps and the surface shows single atomic steps corresponding to a layer-by-layer growth. For thicker Ni/Cu(100) films, nanometer-size clusters are randomly distributed on the surface showing a three-dimensional island growth. For thinner Ni layers in the coherent region, the magnetic anisotropy energy of the Cl-electrolyte/Ni interface is small. The reduction of squareness of the hysteresis loops is related to the inhomogeneous growth of the Ni layers. For thicker Ni layers in the incoherent region, the negative value of interface anisotropy for the Cl-electrolyte/Ni interface has a strong impact on perpendicular magnetic anisotropy and plays an important role on the reduction of the Ni thickness for spin reorientation transition in the electrolyte condition. By adding Pb additives, the deposition of a Pb wetting layer causes a defaceting phenomenon and the hydrogen evolution reaction is reduced. As the Ni thickness increases, the growth of Ni changes from layer-by-layer to quasi-two-dimensional islands with a flat top layer. With a Pb additive, the spin reorientation transitions of the Ni/Cu(100) system are not significantly influenced. However, due to the change of the growth mode by Pb atoms as a surfactant, the squareness of the hysteresis loops is enhanced for all the Ni thicknesses.

Tuning coercive force by adjusting electric potential in solution processed Co/Pt(111) and the mechanism involved

“…The diameter of the crystal is 8 mm while the thickness is 2 mm. This specimen size is suitable for the designed apparatus for the MOKE measurements in electrochemical environments283556. Before loading into the electrochemical cell, the surface of the crystal was mechanically polished with alumina powder with a diameter down to 0.05 μm and was then annealed using a hydrogen torch.…”

“…To avoid contamination by oxygen, the solutions were purged with high purity argon for 1 hr before the experiments. The electrochemical cell used for the CV and MOKE measurements was developed and built in our laboratory3456. Pt and Ag wires were used as the counter electrode and the reference electrode, respectively.…”

“…Pt and Ag wires were used as the counter electrode and the reference electrode, respectively. The electricity of the standard three-electrode setup was controlled by a potentiostat that was constructed in Bonn34566061. The CV of the Pt(111) electrode in a pure supporting electrolyte containing HCl and KCl, and with a CoCl 2 additive are shown in the Supplementary Information 1.…”

Layered structure and related magnetic properties for annealed Fe/Ir(111) ultrathin films

“…The investigations of well-controlled transition metals on metallic substrates are an important topic in material science because of their scientific significance as well as technological applications, especially in surface alloying, microelectronics, enhancing catalytic activities, and spintronics. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] For instance, adsorption of oxygen on Ag/Pt(111) surface alloy leads to an attractive interaction between adsorbed oxygen atoms while oxygen adsorption is blocked on Ag sites. 1 By optimizing the Pt surface content or the Pt film thickness, unambiguous demonstrations of bimetallic surfaces reaching activities well in excess of that of Pt(111) have been made.…”

“…3 The negative interface anisotropy for the Cl-electrolyte/Ni interface plays an important role on the reduction of the Ni thickness for spin reorientation transition in the electrolyte condition. 5 Iridium is widely used in electrochemistry as preferred metal electrode material while iron and iron-based alloys are the most important materials in magnetic industry. Concerning the investigations of iron on iridium substrates, they show brilliant potentials for the applications in electrochemistry and magnetism, and some interesting phenomena can be found in the literature.…”