Lecture Marti Gich
|15 December 2005||FWN-Building 5118.-152, Nijenborgh 4, 9747 AG, Groningen|
|Speaker:||Dr. Marti Gich|
|Affiliation:||Institut de Ciència de Materials de Barcelona, Campus Universitat Autònoma de Barcelona|
|Title:||Magnetoelectric coupling in ε-Fe2O3 nanoparticles|
|Date:||Thu Dec 15, 2005|
|Telephone:||+31 50 363 4565|
Among the iron (III) oxides, ε-Fe2O3 is one of the rarest and less studied polymorphs due to the difficulty to synthesize it as a single-phase or as a large single crystal. Recently, pure ε-Fe2O3 nanoparticles were prepared by sol-gel synthesis . Interestingly, ε-Fe2O3 has an orthorhombic non-centrosymmetric structure (space group Pna2 1 ) which is isomorphous to that of the piezoelectric, ferrimagnetic and magnetoelectric GaFeO3. At room temperature, ε-Fe2O3 is a ferrimagnet with a large coercivity (20 kOe). More remarkably, upon cooling, a strong reduction of the coercivity and the squareness ratio, MR/M S is observed at T ~ 100 K which is ascribed to a magnetic transition also involving structural changes. I will like to report on dielectric permittivity data as a function of temperature, frequency and magnetic field. Relative changes in dielectric constant as large as 30 % have been measured along the temperature range of the magnetic transition evidencing the existence of a magnetoelectric coupling in this material. A ferric oxide such as ε-Fe2O3 would have significant advantages over the Bi or Mn-based biferroic materials, in terms of control of stoichiometry and current leakages due to its more stable chemical composition.
 M. Popovici, M. Gich, D. Niźňanský, A. Roig, C. Savii, Ll. Casas, E. Molins, K. Zaveta, C. Enache, J. Sort, S. de Brion, G. Chouteau and J. Nogués, Chem. Mater.
16, 5542 (2004).
 M. Gich, A. Roig, C. Frontera, E. Molins, M. Popovici, J. Sort, G. Chouteau, D. Martín y Marero and J. Nogués, J. Appl. Phys. 98, 044307 (2005).
|Last modified:||22 October 2012 2.30 p.m.|