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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
Start: 14.00
Location: FWN-Building 5118.-152
Host: B. Noheda
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 [1]. 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.

[1] 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).
[2] 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).


Laatst gewijzigd:22 oktober 2012 14:30