Magnetization of Fe‐oxide based nanocomposite tuned by surface charging

Abstract

Aiming at a voltage‐control of magnetism, the magnetization of a porous γ‐Fe2O3–Pt nanocomposite is studied under the influence of charging the surfaces of the porous structure in an electrolyte. Reversible variations of the magnetization of up to 10.4% could be achieved upon charging in the regime where electrochemical adsorption and desorption occurs. The observed variation of the magnetization with electrochemical charging is assigned to the γ‐Fe2O3 nanoparticles whereas the conductive network of Pt nanoparticles is necessary for charging. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

SQUID magnetometry combined with in situ cyclic voltammetry: A case study of tunable magnetism of γ-Fe2O3 nanoparticles

“…In the high potential range between +150 and +300 mV a only faint oscillation can be discerned. In agreement with our earlier results [8] the magnetic moment increases with negative charging and decreases with positive charging with extrema close to the potential limits. A slight linear drift is superimposed to the variation of m , the sign and slope of which depend on the scanned potential range.…”

“…Irrespective of the potential range studied in advance, the same variation of m is observed in both cases. The magnitude of the m variation of up to 4.2% of $\gamma$-Fe 2 O 3 /Pt-nanocomposite is also in reasonable agreement with our previous measurements on other $\gamma$-Fe 2 O 3 /Pt samples in the two-electrode set-up [8].…”

“…To demonstrate the functionality of this measuring set-up, we have examined the tunability of the magnetism of $\gamma$-Fe 2 O 3 nanoparticles. In a previous work we could show that the magnetic moment of $\gamma$-Fe 2 O 3 nanoparticles can be varied reversibly up to several percent upon electrochemical charging [8]. By means of the three-electrode cell used in the present study detailed information on the correlation between the electrochemical processes and the magnetic behaviour can be derived.…”

“…In the case of electrodeposition such in situ measurements were performed with the help of magneto-optical Kerr effect [2,11,12] and alternating gradient field magnetometry [2,13]. In situ studies of the charging-induced modification of magnetic properties of materials were performed by magneto-optical Kerr [9] or Faraday effect [10] as well as by magnetometry using extraction magnetometers [3–7] or a SQUID magnetometer [8]. Most of these measurements were performed with electrochemical cells containing only two electrodes [3–6,8,9].…”

Sign-inversion of charging-induced variation of electrical resistance of nanoporous platinum

“…In this way, voltage-induced reversible variations of the lattice spacing and macroscopic length [1] or, for instance, of the magnetic behavior [2,3] of cluster-assembled porous nanocrystalline metals could be demonstrated. Even the properties of nanocrystalline oxides, e.g., the magnetic moment, can be modified via surface charging upon mixing the oxide nanoparticles with a porous conductive network of metallic nanoparticles for electrochemical charging [4].…”