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Dipartimento di Fisica e Scienze della Terra

Multiferroic materials

Involved People: Massimo Solzi, Roberto De Renzi, Giuseppe Allodi

in collaboration with:

E. Gilioli, D. Delmonte, R. Cabassi, F. Bolzoni (IMEM-CNR Institute, Parma)

G. Calestani, L. Righi, F. Mezzadri, (Dept. of Chemistry, Parma University)

F. Orlandi (ISIS-Rutherford Appleton Laboratory, Oxford, UK)

The multiferroics represents an interesting class of materials in which coexist at least two ferroic orders between ferroelectricity, ferromagnetism and ferroelasticity. In particular, the magnetoelectric (ME) multiferroics may potentially achieve a significant technological impact, allowing the realization of multifunctional devices with crossed electrical and magnetic control. Apart from the possible applications, the combination of magnetism and ferroelectricity in a single-phase material is a great challenge even in fundamental science, where it is still an open question that concerning the understanding of the coexistence of the two ferroic orders, which in principle are mutually excluding, and their complex coupling mechanisms. In this scenario, the compounds with perovskite structure represent a promising playground, for the particular ability of this structure to host atomic species with different ionic radii and different functionality through the lattice distortion. In particular, several manganites with perovskite structure (with general formula AMnO3) show magneto-electric properties, in some cases due to the high magneto-electric coupling or to the multiferroicity above room temperature.

This research line involves the synthesis of compounds with perovskite structure under conditions of high pressure and high temperature, using a Multianvil Walker-type press (IMEM-CNR), which allows to work at very high isotropic pressure (up to 25 GPa) and temperatures up to 2500 °C. In this thermodynamic regime, almost completely unexplored, compounds never realized previously can be synthesized as metastable phases. The study of electrical, magnetic and magnetoelectric properties of these materials is highly complex and requires the use of unconventional techniques for their characterization. At DiFeST one can perform the standard magnetic characterization of realized materials, using SQUID magnetometry and ac susceptometry. Moreover dynamic measurements of ferroelectric hysteresis, leakage current and capacitance, using the AIXACCT TF Analyzer 2000E system; measurement of magnetoelectric and electrical properties (permittivity, resistivity and pyroelectricity) under magnetic field, using probes specifically designed to be integrated into the SQUID magnetometer.