Magnetic and Dielectric Properties of CaMn7 O12 Thin Films Grown by Pulsed Laser Deposition
Recently, the multiferroic materials with the coexisting electric polarization and long-range magnetic order have been extensively studied. Among the large array of multiferroic materials, CaMn7O12 stands out as one of the most promising novel multiferroic materials owing to its pronounced magnetism-induced ferroelectric polarization recently reported. There are two phase transitions(TN1=90K、TN2=48K) observed both in ceramic and single crystal of rhombohedral CaMn7O12. CaMn7O12 reveals a giant improper ferroelectric polarization strongly coupled to the magnetic structure at rather high Neel temperature (first phase transition), 90K, which is oriented parallel to the c axis. As the ferroelectric polarization is oriented parallel to the c axis, we grew the thin film of CaMn7O12 on Nb-doped SrTiO3 by pulsed laser deposition. It is expected that in thin film form not only the intrinsic magnetism-induced ferroelectric polarization can be unveiled but also the potential applications of this intriguing material can be demonstrated. X-ray diffraction was used to reveal the phase structure of the films deposited on NSTO substrates prepared under various conditions. Magnetic susceptibility measurements were performed using Superconducting Quantum Interference Device (SQUID) to delineate the magnetic properties of the films and their correlations with electric properties. Characterizations on electric transport and dielectric properties as a function of temperature will be presented and discussed.
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