Coercivity Control of Variable-Length Iron Chains in Phthalocyanine Thin Films

Abstract

The magnetic characteristics of iron phthalocyanine thin films are studied with a vibrating sample magnetometer, identifying a ferromagnetic transition temperature at 4.5 K. The metal ions at the center of the molecule are self-assembled along chains producing quasi one-dimensional magnetic chains of variable length in the thin films. The average chain length is varied from 20 to 300 nm via substrate temperature during deposition. Below the critical transition temperature, the magnetization curves have the shape of wasp-waisted or constricted loops. The inplane chain length modulates the coercivity and saturation field and larger grains increase the coercivity significantly. First-order reversal curves of the wasp-waisted hysteresis loops reveal a long narrow strip that suggests a broad distribution of coercive fields and weak intergrain magnetic interactions. These findings are also supported through simulations based on the Preisach model.

Controlling Ferromagnetic Ground States and Solitons in Thin Films and Nanowires Built from Iron Phthalocyanine Chains

“…Increasing the crystallinity of the films and grain size has already been shown to have a large effect on the magnetic properties . These effects can be further explored with the FePc nanowires.…”

“…We then investigate FePc nanowires, which represent a particularly interesting system as the chain length can be up to five orders of magnitude larger than for the films, a configuration that significantly improves the electronic transport properties . It has already been shown that the length of the iron chains also strongly influences the magnetic properties, with an increase in coercive field observed for increasing crystal size . Therefore, new behaviors are expected for FePc nanowires with the magnetic anisotropy of the molecular plane competing with the shape anisotropy of the nanowires.…”

“…TEM images and digital diffractograms, shown in the insets, of single wires obtained in the c) (200) and d) (001) projections. e) Normalized UV–vis absorption of η‐ and α‐FePc (continuous lines), with the equivalent CuPc spectra (dashed lines) shown for comparison and f) XRD scan (acquired for 80 s per step) for nanowires together with a simulated scan with a peak broadening of 2θ = 0.2° in red . g) Linescan of the intensity for the wire shown in (c), highlighting the (200) lattice spacing and h) an HRTEM image with expected molecular arrangement.…”

Modeling the Magnetic Properties of 1D Arrays of FePc Molecules

“…In this work, we refer to this polymorphism as α + . FePc TFs have been reported to become ferromagnetically correlated at temperatures below 20 K 14 and exhibit a ferromagnetic transition at 4.5 K, very similar to the transition temperature in powders at 5 K …”

Time resolved FORC analysis and magnetic anisotropy in K0.4[Cr(CN)6][Mn(S)-pn] (S)-pnH0.6 chiral molecular magnets

“…A fruitful and powerful method to distinguish different types of spin configurations is the first order reversal curves (FORC) method well developed theoretically [17][18][19] and tested experimentally for inorganic ferromagnets [20,21], and metal-organic films [22]. A method similar to the FORC one and applicable to thermal hysteresis was developed for single molecular complexes [23][24][25] and microparticles [26].…”