J. Phys. IV France 114 (2004) 125
Low frequency dielectric properties in a ferromagnetic semiconductor (ED-TTFVO) 2FeBr 4 with permanent electric dipolesE. Negishi1, S. Yabuta1, T. Matsumoto2, T. Sugimoto2 and N. Toyota1
1 Physics Department, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
2 Research Institute for Advanced Science and Technology, Osaka Prefecture University, Osaka 599-8570, Japan
We have measured the dielectric constant 1 and conductivity 1 along the b-axis in a ferromagnetic ( K) semiconductor (ED-TTFVO) 2FeBr 4 with permanent electric dipoles, using a three-terminal capacitance bridge at frequencies from 10 Hz to 2.8 kHz at excitation voltages from 25-250 mV. The temperature dependence of 1, which is as large as 10 4 - 105, shows a broad peak at Tp associated with a hump at below . These two anomalous temperatures increase with frequency; K (10 Hz)-40 K (2.8 kHz) and K (10 Hz)-17 K (2.8 kHz). Furthermore, 1 and 1 exhibit a remarkable non-linearity with the excitation voltage. These characteristic behaviors are reminiscent of a ferroelectric relaxor. Key words. (ED-TTFVO) 2FeBr 4, Dielectric constant, Molecular electric dipoles, system, Ferromagnetism, Ferroelectric relaxor.
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