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Antiferromagnets are magnetically ordered, but neighboring magnetic moments point in opposite directions, which results in zero net magnetization. This property makes them promising for future spintronic applications, since antiferromagnets produce no stray fields and are insensitive to external magnetic field perturbations. In addition, they show intrinsic dynamics in the terahertz range and exhibit considerable spin-orbit and magneto-transport effects. The above could allow the creation of high-density memories with no inter-bit dipole interactions and fast write times, as well as the development of compact room-temperature terahertz sources and detectors1,2. In this work, we will present the investigation of L10 MnPt antiferromagnetic thin films. The films consist of Pt/Mn multilayers, sputter-deposited onto commercial oxidized Si wafers. X-ray diffraction (XRD) characterization shows the emergence of the chemically-ordered L10 MnPt crystal structure after annealing the samples at temperatures 400oC or higher (see figure 1). Secondary ion mass spectroscopy (SIMS) shows the layered structure of the as-deposited stack, which thereafter transforms into an alloy film after annealing (see figure 2). Our initial findings are promising and static magnetic characterization by means of magnetometry and magnetic force microscopy will be also presented

Two different nanostructures are studied in this contribution: large-area nanopillar arrays fabricated by glancing angle deposition with magnetron sputtering (MS-GLAD) and magnetic thin films perforated with long-range order arrays of nanoholes prepared by focused ion beam (patterned antidots). MS-GLAD is an easy and versatile route to fabricate arrays of nanostructures in large areas in a single processing step. In our work, nanostructured films with vertical or tilted nanopillars composed by polycrystalline Fe and Fe2O3 have been fabricated depending on whether the substrate is kept rotating azimuthally during deposition or not, respectively [1]. The magnetic properties of these films can be tuned with the specific morphology. In particular, the growth performed through a collimator mask mounted onto a not rotating azimuthally substrate produces almost isolated well-defined tilted nanopillars that exhibit a magnetic hardening. The first-order reversal curves diagrams and micromagnetic simulations revealed that a growth-induced uniaxial anisotropy, associated with an anisotropic surface morphology produced by the GLAD in the direction perpendicular to the atomic flux, plays an important role in the observed magnetic signatures. Magnetic antidots are being studied for different applications, such as magnonic crystals for microwave devices, magnetically-active plasmonic media, magnetic biosensing, and magneto-resistance sensors. In our work, a top-down approach using focused ion beam has been employed to fabricate Co/Permalloy hard-soft bilayer antidot arrays [2]. The antidots have a 40 nm diameter and two symmetries are studied: square and hexagonal. A dependence of magnetic coercivity on the relative thicknesses of the magnetically hard (Co) and soft (Permalloy) layers is found; increasing Permalloy thickness results in lower magnetic coercivity. Furthermore, the long-range periodicity of these antidots results in higher magnetic coercivity and a stronger magnetic

A top-down approach using focused ion beam has been employed to fabricate Co/Permalloy hard-soft bilayer magnetic antidot arrays. These nanopatterned films are studied with particular emphasis on magnetic coercivity. The antidots have a diameter of 40 nm and the studied antidot symmetries are square and hexagonal. A dependence of magnetic coercivity on the relative thicknesses of the magnetically hard (Co) and soft (Permalloy) layers is found; increasing Permalloy thickness results in lower magnetic coercivity. Furthermore, the long-range periodicity of top-down nanopatterned antidots results in higher magnetic coercivity and a stronger magnetic domain-wall pinning, compared to identical hard/soft bilayers of short-range order deposited on porous anodic alumina. The combination of antidot symmetry and hard/soft thickness, allow for efficient tailoring of the magnetic properties of nanopatterned thin films. Finally, magnetic force microscopy imaging of the antidot array magnetic configuration shows striking qualitative differences between the two array symmetries: square symmetry arrays have inhomogeneous magnetic state and a high density of immobile super-domain walls, whereas hexagonal symmetry arrays show a homogeneous magnetic configuration.

We report on the static and dynamic magnetic properties of W/CoFeB/Ta/CoFeB/MgO stacks, where the CoFeB layer is split in two by a 0.3 nm-thick Ta “dusting” layer. A total CoFeB thickness between 1.2 and 2.4 nm is studied. Perpendicular magnetic anisotropy is obtained for thickness below 1.8 nm even at the as-deposited stacks, and it is enhanced after annealing. Saturation magnetization is 1520 (1440) kA/m before (after) annealing, increased compared to non-split CoFeB layers. Ferromagnetic resonance measurements show that high magnetic anisotropy energy may be achieved (effective anisotropy field 0.571 ± 0.003 T), combined to a moderate Gilbert damping (0.030 ± 0.001). We argue that the above characteristics make the split-CoFeB system advantageous for spintronics applications.

The effect of different spacer materials (MgO, W, and Pt) on the magnetic coupling in FePt/spacer/FePt trilayers has been carefully investigated. MgO results in magnetically coupled FePt layers with perpendicular magnetic anisotropy (PMA); W gives rise to a magnetically coupled system consisting of layers with PMA and in-plane magnetic anisotropy whereas Pt results in magnetically decoupled FePt layers with PMA. The trilayer microstructure is essential for explaining the obtained results. The growth mode of the top FePt layer is strongly affected by the underlying non-magnetic spacer, with occurrence of different morphologies; in particular, L10 FePt islands grow on MgO, a continuous FePt layer with fcc crystal structure is obtained on W, whereas a continuous layer with L10 structure is observed when the top layer is deposited on Pt.

We study metal-coated paper for low cost sensor applications. Sputter deposition is used to coat commercially available stationary printer paper with Au or Ag thin films. Two kinds of substrates are used: copy paper and glossy photo paper. The surface morphology, coating structure and electrical resistivity of the samples is studied. We find that after deposition of a nominally 100 nm thick metal layer the templates retain their initial morphology, which is fibre-like at the copy paper and flake-like at the photo paper. The metal-coated paper is conductive in both cases, with resistivity a few times higher than the bulk value. The photo paper samples have lower resistivity than the copy paper ones. Moreover, no observable resistivity variation is observed after 8 weeks of room temperature storage in a desiccator.

Nowadays there is an urgent need for enhancing data storage capacity of hard disk drives due to the rapid increase of digital data volume produced worldwide. New effective approaches are required to push the recording areal density beyond the limit of 1 Tbit/in2 of state-of-art hard disk drives. A promising alternative is 3D-magnetic recording, where stacking magnetic layers with different magnetic properties are used [1]. In this work we report on the morpho-structural and magnetic properties of FePt/interlayer (MgO, Pt or W) /FePt magnetron sputtered trilayers, as a base structure towards 3D magnetic recording systems. The stack is grown on an MgO (100) substrate and consists of two magnetically hard FePt layers with a thickness of 20 and 10 nm separated by an interlayer of variable thickness (5 up to 50 nm). Fig 1a summarizes the coercivity for all MgO, W or Pt interlayer samples; the layers seem to be coupled even at 20 nm of MgO or W interlayer thickness. However, at 5 nm interlayer thickness, hysteresis loops for W or MgO interlayers are those of a film stack of partially coupled ferromagnetic layers( Figure 1b), whereas a fully decoupled magnetic trilayer is obtained for a Pt interlayer, in agreement to previous reports [2] and also supported by magnetic force microscopy imaging. Finally, electron diffraction patterns and dark field images analysis indicate that most of FePt grains grow in the L10 phase with the (001) planes parallel to the substrate and the MgO interlayer grows oriented as the substrate.

We report on the study of arrays of 60 nm wide cobalt antidots, nanopatterned using focused ion beam milling. Square and hexagonal symmetry arrays have been studied, with varying antidot densities and lattice constant from 150 up to 300 nm. We find a strong increase of the arrays' magnetic coercivity with respect to the unpatterned film, which is monotonic as the antidot density increases. Additionally, there is a strong influence of the array symmetry to the in-plane magnetic anisotropy: square arrays exhibit fourfold symmetry and hexagonal arrays exhibit sixfold symmetry. The above findings are corroborated by magnetic imaging and micromagnetic modeling, which show the magnetic structure of the arrays to depend strongly on the array morphology.

The effect of arrays of nanometer scale pores on the magnetic properties of thin films has been analyzed. Particularly, we investigated the influence of the out-of-plane magnetization component created by the nanopores on the in-plane magnetic behavior of patterned hard/soft magnetic thin films in antidot morphology. Its influence on the coupling in Co/Py bilayers of few tens of nanometer thick is compared for disordered and ordered antidots of 35-nm diameter. The combination of magneto-optical Kerr effect (MOKE) and first-order reversal curve (FORC) technique allows probing the effects of the induced perpendicular magnetization component on the bilayer magnetic behavior, while magnetic force microscopy (MFM) is used to image it. We found that ordered antidots yield a stronger out-of-plane component than disordered ones, influencing in a similar manner the hard layer global in-plane magnetic behavior if with a thin or without soft layer. However, its influence changes with a thicker soft layer, which may be an indication of a weaker coupling

Magnetic antidot arrays are groups of ordered holes patterned on a continuous magnetic film. They can be used as magnonic crystals with potential application in microwave devices [1], for magnetically-active plasmonics [2], and for biosensing applications [3]. We have followed two different routes to obtain magnetic antidots on Co, Permalloy (Py), and Co/Py films with different characteristics. Focused ion beam allowed obtaining hexagonal or square lattice antidot arrays with long-range order (hole diameter d=55nm, periodicity p=150-300nm) [4], whereas oblique deposition onto nanoporous alumina templates was used to obtain arrays with only hexagonal short-range order (d=40nm, p=105nm) [5]. The arrays were studied by magneto-optic Kerr effect, magnetic force microscopy (MFM) and micromagnetic simulations. It is shown how the coercivity increases with the density of antidots and the magnetic anisotropy axes strongly depend on the array symmetry. The MFM images show the magnetic structure of the arrays to be commensurate to their morphology, with domain walls (DW) pinned by the holes and in some cases super-DW separating linear domains (see Fig.).

The emergence of perpendicular magnetic anisotropy (PMA) in CoFeB/MgO stacks deposited on W using a Ta buffer layer is studied as a function of Ta and CoFeB layer thickness and annealing temperature. It is shown that very thin Ta “dusting” layers (thickness between 0.3 and 1 nm) enhance PMA of CoFeB layers grown on top of W. We find that Ta thickness is a crucial factor affecting magnetic anisotropy and it needs to be scaled proportionally to CoFeB thickness for obtaining PMA. Stacks without Ta have in-plane anisotropy, verifying the “PMA-enhancing” role of Ta. The maximum effective PMA energy (3.6×106 erg/cm3) is obtained for a stack with 1.4 nm of CoFeB and 1 nm of Ta and after annealing at 350 °C. Besides, PMA can be obtained even at the as-deposited state for certain thicknesses. This W-based CoFeB/MgO system could enable the development of low power consumption, high density, and non-volatile magnetic memories.