Manipulation of spin state of iron porphyrin by chemisorption on magnetic substrates

Abstract

One of the key factors behind the rapid evolution of molecular spintronics is the efficient realization of spin manipulation of organic molecules with a magnetic center. The spin state of such molecules may depend crucially on the interaction with the substrate on which they are adsorbed. In this paper we demonstrate, using ab initio density functional calculations, that the stabilization of a high spin state of an iron porphyrin (FeP) molecule can be achieved via chemisorption on magnetic substrates of different species and orientations, viz., Co(001), Ni(001), Ni(110), and Ni(111). The signature of chemisorption of FeP on magnetic substrates is evident from broad features in N K x-ray absorption (XA) and Fe L 2,3 x-ray magnetic circular dichroism (XMCD) measurements. Our theoretical calculations show that the strong covalent interaction with the substrate increases Fe-N bond lengths in FeP and hence a switching to a high spin state (S = 2) from an intermediate spin state (S = 1) is achieved. Due to chemisorption, ferromagnetic exchange interaction is established through a direct exchange between Fe and substrate magnetic atoms as well as through an indirect exchange via the N atoms in FeP. The mechanism of exchange interaction is further analyzed by considering structural models constructed from ab initio calculations. Also, it is found that the exchange interaction between Fe in FeP and a Ni substrate is almost 4 times smaller than with a Co substrate. Finally, we illustrate the possibility of detecting a change in the molecular spin state by XMCD, Raman spectroscopy, and spin-polarized scanning tunneling microscopy.

Comparative study of electronic and magnetic properties of iron and cobalt phthalocyanine molecules physisorbed on two-dimensional MoS2 and graphene

“…The efficient spin manipulation has made these molecules an attractive choice for various kind of spin dependent electronics applications. [1][2][3][4] Metal phthalocyanines (M Pc) are porphyrinoid macrocyclic complexes and symmetric organic molecules with a metal atom (M ) at the center surrounded by four bonded N atom and four non bonded N atom. The phthalocyanine molecules do not have any out-of-plane ligands.…”

Coupling of single, double, and triple-decker metal-phthalocyanine complexes to ferromagnetic and antiferromagnetic substrates

“…Despite such differences, for all planar molecules investigated to date, the interaction between the magnetic moment of the molecules and that of metal substrates has been found to be FM (see Table 1). This has been attributed to the direct exchange path between the central metal ion and the substrate atoms as well as to an indirect superexchange path via the N atoms [29,43]. Only when O or graphene is intercalated between the molecules and the substrates the coupling has been found to be AFM (see Table 1).…”

Fen(n=1–6) clusters chemisorbed on vacancy defects in graphene: Stability, spin-dipole moment, and magnetic anisotropy

“…It is usually neglected for bulk systems with high symmetry. Recently, it has been shown that, for lowdimensional systems, e.g., clusters [24] and organometallic molecules with magnetic centers [18,25,26], this contribution, commonly denoted as T z , has a significant role. More interestingly, the spin-dipole contribution may have an opposite sign to that of spin moment, thereby reducing the effective moment (m eff = m s + 7 T z ), which is measured in XMCD experiments [27].…”