The magnetization state of electrodeposited Fe/Au(1 1 1) layers is investigated during the growth using in situ alternating gradient force magnetometry. It is shown that perpendicular magnetization anisotropy occurs as long as the thickness tFe<2 ML. The effect of depositing Cu on top is also studied. Results are compared to those obtained with MBE layers and discussed in the light of preliminary STM investigations of Fe growth.

Co/Pd multilayers deposited on Si (111) by electron gun evaporation were investigated. The magnetization measurements indicated out-of-plane easy magnetization direction for the samples with small Co layer thickness. The normal-to-the-plane remanent magnetization curves of the sample with Co layer thickness of 4 show four well-defined levels depending on the field strength and direction. Each of these levels can be obtained by applying a broad range of fields making them easily accessible, and the high field remanence levels are lower in intensity than the low field ones. This seems to be an effect of competing magnetic anisotropies of different nature present in the samples. The coercive and switching fields, the remanence and all others technological requirements may eventually be tailored for a proper high-density recording media. (C) 2001 Elsevier Science B.V. All rights reserved.

The magnetization state of electrodeposited Fe/Au(1 1 1) layers is investigated during the growth using in situ alternating gradient force magnetometry. It is shown that perpendicular magnetization anisotropy occurs as long as the thickness t(Fe) < 2 M L. The effect of depositing Cu on top is also studied. Results are compared to those obtained with MBE layers and discussed in the light of preliminary STM investigations of Fe growth. (C) 2001 Elsevier Science B.V. All rights reserved.

The magnetization state of electrodeposited Fe/Au(111) layers is investigated during the growth using in situ alternating gradient force magnetometry. It is shown that perpendicular magnetization anisotropy occurs as long as the thickness tFe<2ML. The effect of depositing Cu on top is also studied. Results are compared to those obtained with MBE layers and discussed in the light of preliminary STM investigations of Fe growth.

The magnetization state of electrodeposited Fe/Au(1 1 1) layers is investigated during the growth using in situ alternating gradient force magnetometry. It is shown that perpendicular magnetization anisotropy occurs as long as the thickness t Fe <2 ML. The effect of depositing Cu on top is also studied. Results are compared to those obtained with MBE layers and discussed in the light of preliminary STM investigations of Fe growth. Keywords Anisotropy Electrodeposition It is well known that the magnetic moment of Fe atoms greatly depends on the crystal structure (FCC versus BCC) and its lattice parameter [1] . Therefore this makes the comparison of films prepared by different techniques highly interesting to eventually correlate different structure to the magnetic state. This work is a preliminary study of electrodeposited Fe/Au(1 1 1) layers. An in situ alternating gradient force magnetometer (AGFM) set-up was developed where the sample is immersed in an electrochemical cell and connected to a potentiostat for well-defined electrochemistry. The perpendicular ( M ⊥ ) and parallel ( M ∥ ) components of the magnetization may be probed from the very initial stages of the metal growth. Hysteresis loops can also be recorded. As shown below, results indicate that the occurrence of perpendicular magnetization anisotropy (PMA) depends on the surface chemistry of Fe. The top of Fig. 1 gives the electrochemical response of the gold electrode in a 1 mM FeSO 4 solution of pH 4 (potentials are quoted versus the Hg/Hg 2 SO 4 reference electrode). The samples consisted of textured Au(1 1 1) 100 nm-thick-films evaporated on mica that were flame annealed before use to obtain the 22×√3 surface reconstruction [2] . Fig. 1 indicates that deposition occurs for U <−1.45 V. Stripping of the layer is monitored by reversing the potential scan ( U >−1.2 V). Integration of the charge Q under the anodic peak was used to derive the iron thickness, assuming the reaction Fe→Fe 2+ +2e − [1 ML of γ–Fe(1 1 1) Q=560 μC/cm 2 ]. The negative wave at −1.3 V is the reduction of protons. The bottom panel of Fig. 1 shows the transients of the magnetization M ⊥ (t) and M ∥ (t) recorded during Fe deposition at U =−1.45 V ( t >20 s). No external field H 0 was applied (remanent field between poles is 30–50 Oe). The primary information is the ferromagnetic state of the iron layer at room temperature for a thickness well below t Fe <4–5 ML (this is the thickness measured after 50 s of deposition). The second remark is the occurrence of PMA for t Fe <1.8 ML. In fact, M ⊥ (t) peaks at t =42 s while M ∥ (t) remains zero over the same time. Note that the delay between the step of potential ( t =20 s) and the detection of an M ⊥ (t) signal ( t =27 s) is attributed to the progressive nucleation of the Fe layer. As the film thickness increases, M switches to become totally in-plane ( M ⊥ (t)=0 ). This transition is completed above a critical thickness t Fe * ∼2.5 ML. The hysteresis loops (HL) displayed in Fig. 2 were obtained after stopping deposition by setting U =−1.25 V (the deposit neither grows further nor dissolves). The Fe thickness was ∼1.5 ML. Bold symbols correspond to the naked Fe layer. With H ⊥ the square and open ( H C =50 Oe) loop is a confirmation of PMA. The corresponding HL is reversible with H ∥ . For thicker layers ( t Fe >2 ML) reversible HL's are obtained with H ⊥ and square ones with H ∥ (not shown). The experiment in Fig. 2 was continued by depositing in situ a Cu layer atop the Fe film (trace amounts of CuSO 4 , were added to solution, still keeping the potential U =−1.25 V, so as to obtain a thin Cu deposit, without exposing the Fe to air). The resulting HL's (open symbols) indicate that M becomes in-plane upon Cu deposition. The results above demonstrate that electrodeposited Fe layers exhibit remarkable magnetic properties at room temperature , showing ferromagnetism down to 1 ML equivalent thickness. This is in contrast with evaporated Fe(1 1 0) layers on Au(1 1 1) [3] and pulsed laser layer deposited Fe(1 1 1) films on Cu(1 1 1) [4] for which the Curie temperature remains well below RT. Given Ref. [1] and preliminary in situ STM observations which indicate that Fe grows nearly layer by layer up to 4–5 ML [2] , we suspect that FCC γ–Fe(1 1 1) layers are growing electrochemically. From STM there is no clear indication of a phase transition γ–Fe(1 1 1)→α–Fe(1 1 1) below 5 ML thickness. Such a transition occurs around 3 ML during MBE deposition [5,6] . This difference is attributed to the possible formation of an anion layer at the Fe/Solution interface. This layer likely stabilizes the metastable γ phase under tensile stress since anion layers often generate compressive stress on metallic layers. Under this hypothesis, the disappearance of the PMA after Cu deposition ( Fig. 2 , open symbols) might arise from a phase transition inside the Fe layer. Namely, the removal of the anionic layer would lead to collapse of the metastable Fe/Au structure. References [1] F.J. Himpsel Adv. Phys. 47 1998 511 [2] T. Okuyama Jpn. J. Appl. Phys. 30 1991 2053 [3] P. Ohresser Phys. Rev. B 59 1999 3696 [4] L. Cagnon, P. Allongue, unpublished work. [5] B. Voigtländer Surf. Sci. 255 1991 L529 [6] J.A. Strocio J. Vac. Sci. Technol. A 10 1992 1981

This work investigates the structure and interface perpendicular magnetic anisotropy (PMA) of electrodeposited Cu/Co/Au(111) sandwiches with variable Co thickness [2-20 monolayers (ML's)]. In optimum deposition conditions, polar magneto-optical Kerr effect measurements show that the axis of easy magnetization is perpendicular to the layers for thicknesses below ca. 7.2 ML's. This value is among the best ever reported for the Cu/Co/Au(111) structure. While extended x-ray-absorption fine structure indicates that layers are hcp, in situ STM imaging suggests that magnetoelastic effects contribute significantly to PMA. The correlation observed between the strength of PMA and film structure is discussed in details.

This work presents preliminary in-situ alternating gradient field magnetometry measurements at the electrochemical interface. The technique is used for the first time for real time determination of the magnetic state of ultrathin layers during their electrochemical growth. Electrochemical measurements complement this study and structural information, using in-situ STM, is presented to discuss the magnetic behavior of the different films. Particular attention is given to magnetization anisotropy, and the results give evidence for strong differences between M/Au(111) interfaces, with M = Co. Ni and Fe. The easy axis of magnetization is in-plane for nickel, regardless of the film thickness, whereas the magnetization is out-of-plane for cobalt and iron below a critical thickness t* approximate to 1-2 and 2-3 ML respectively. Above t* the magnetization rotates to take the in-plane orientation.

In-situ scanning tunneling microscopy (STM) and in-situ alternating gradient field magnetometry (AGFM) are used in combination to characterize the structure and magnetic behavior of Co/Au(111) layers electrodeposited from CoSO4 solutions, with anions X=Cl− and SCN− added in amount traces. In the Cl− solution, the 2-D growth process is briefly recalled. In the thiocyanate (SCN−) solution, preliminary observations show that nanometer clusters accumulate on top of a Co underpotential deposition (UPD) monolayer. Both structures solution/Co/Au(111) exhibit perpendicular magnetic anisotropy (PMA) for a Co thickness t≤t*, with t*∼2 ML in the Cl− solution and ∼4–5 ML in the SCN− one. Results are briefly discussed in light of classical models for PMA in ultrathin films.

In the present work we report on the properties of Cu-Co nanometric multilayers electrodeposited on indium-tin oxide (ITO) glass using a single electrolyte and the pulse potential technique. We investigated the effect of the pulse potentials on the magnetism and magnetoresistance. The ITO glass substrate allows the deposition of the multilayers directly on it and the characterization of their properties without separating them from the substrate. Optimal pulse potential ranges are characterized for both copper and cobalt deposition. The multilayers have a high magnetization and a large magnetoresistance ratio. (C) 1999 The Electrochemical Society. S0013-4651(98)07-105-5. All rights reserved.