Self-Assembly and Superexchange Coupling of Magnetic Molecules on Oxygen-Reconstructed Ferromagnetic Thin Film

Abstract

We report on the distinctive molecular assembly and exchange coupling of paramagnetic manganese(III) tetraphenylporphyrin chloride (MnTPPCl) molecules on a metallic cobalt (Co(001)) and on an oxygen-reconstructed cobalt (O/Co(001)) substrate, the latter substrate being prepared by surfactant-mediated growth. For MnTPPCl, a ferromagnetic (FM) exchange coupling to Co(001) and an antiferromagnetic (AFM) exchange coupling to O/Co(001) were identified. The random adsorption of MnTPPCl on Co(001) is turned into a self-assembled and well-ordered 2D molecular domains on O/Co(001). Different oxidation states for Mn ions are found to exist on different substrates. The here presented spectromicroscopy-correlation approach, involving X-ray magnetic circular dichroism (XMCD) spectroscopy, X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy (STM), demonstrates its strength to identify the mechanism involved in organic spintronic interfaces.

Magnetic exchange coupling of a synthetic Co(ii)-complex to a ferromagnetic Ni substrate

“…25 This adsorption behaviour corresponds well to results obtained for Mn, Fe, Co and Ni porphyrins adsorbed on Co(001) and Ni(001) thin films. [3][4][5]14 In the case of the stacking of two complexes onto each other, as observed for a small fraction, the overlapping parts are imaged as brighter protrusions. The magnetic and electronic properties of the ad-complexes are studied by XAS and XMCD spectroscopies.…”

Exchange Interaction of Strongly Anisotropic Tripodal Erbium Single-Ion Magnets with Metallic Surfaces

“…Also, this observation agrees well with the chemisorption observed for several metal-porphyrins on Co and Ni thin films. 37 On Au(111), imaging was only successful at 130 K. At room temperature, it was impossible to obtain stable imaging conditions because of frequent spikes in the tunnel current, which are most likely due to thermal motion or the movement of molecules by the STM tip. These observations are consistent with the physisorption of the molecules as found from the XPS and DFT evidence.…”

Antiferromagnetic coupling of Cr-porphyrin to a bare Co substrate

“…Spin-bearing metal-organic molecules have attracted considerable attention in recent years [1][2][3][4]. In particular, squareplanar coordination complexes offer a wide range of tunable chemical functionalities [5][6][7][8], which derive from the sensitive interaction of the open shell of the metal center with the planar ligands as well as with the surrounding molecular architecture. In "on-surface" configurations novel properties can arise when the magnetic and electronic characteristics of the metal-organic species are subtly modified by the surface-molecule interaction.…”

“…The origin of this alignment has been much discussed [1,2,7,10,11] and assigned either to direct or indirect magnetic exchange coupling via the chemical bonds across the interface. Understanding and controlling molecule-substrate interactions are key ingredients for designing novel functional surfaces [15].To date, an antiferromagnetic (AFM) indirect exchange interaction has been reported for planar molecules assembled on oxygen reconstructed Ni and Co substrates [5,6] or when a graphene interlayer [12] was introduced between the molecule and substrate. An indirect AFM coupling was also observed for the rare-earth double-decker Tb-bis-phthalocyanine adsorbed on a metallic FM substrate, where one macrocycle acts as an interlayer [13].…”

“…In "on-surface" configurations novel properties can arise when the magnetic and electronic characteristics of the metal-organic species are subtly modified by the surface-molecule interaction. Accordingly, it was discovered that metallophthalocyanines and metalloporphyrins with 3d and 4f block metal centers exhibit remarkable electronic, optoelectronic, and magnetic properties when adsorbed on surfaces [1,2, [5][6][7][8][9][10][11][12][13][14][15][16]. Strikingly, the magnetic exchange coupling of the spin of metalloporphyrins or metallophthalocyanines with that of ferromagnetic (FM) substrates (Co and Ni) was found to induce stable magnetic order in the paramagnetic molecules at and above room temperature [1,2,11].…”