Tunable dielectric properties in Mn-doped LuFe 2 O 4 system
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ping Yao, Sining Dong, Xi Huang, Xuefeng Sun, and Xiaoguang Lia) Hefei National Laboratory for Physical Sciences at Microscale, Department of Physics, University of Science and Technology of China, Hefei 230026; and International Center for Materials Physics, Academia Sinica, Shenyang 110015, People’s Republic of China (Received 10 June 2011; accepted 15 December 2011)
The dielectric properties and tunability with external magnetic and electric fields for LuFe2-xMnxO4 (0 # x # 1) are systematically studied. It was found that the dielectric loss, the ferrimagnetic Curie temperature, and the conductivity reduce with increasing Mn doping. One of the most important results is that the room temperature dielectric tunability with low magnetic and electric fields can be achieved in these samples. The analysis demonstrates that the electron transfer between Fe2+ and Fe3+ is efficiently suppressed with Mn doping and thus results in the decreases of the leaky conductivity and the dielectric loss. Furthermore, from the studies on the combination of impedance and modulus complex planes for the samples with different electrodes, the tunability is found to be more closely related to the extrinsic effect than the intrinsic bulk effect.
I. INTRODUCTION
Recently, many efforts have been devoted to searching for materials possessing a high magnetoelectric or magnetodielectric coefficient due to their potential applications such as nonvolatile memories, magnetic read heads, etc.,1 and a number of promising candidates in multiferroics have been reported already.2,3 For example, the bulk LuFe2O4 exhibits a large room temperature dielectric tunability with low external magnetic and electric fields,4,5 opening a possible route for future devices. However, the relatively high dielectric loss in this system apparently limits the applicability.5 Thus, one of the most important issues in this field is how to effectively reduce the dielectric loss. The earlier reports have indicated that the ferroelectricity in LuFe2O4 is closely related to the charge ordering between Fe2+ and Fe3+ ions,6,7 and the electron transfer between the Fe ions plays an essential role in the resistivity and dielectric response,8 which illustrates that the suppression of the electron transfer on Fe site ions could reduce the conductivity and dielectric loss. So one effective route to suppress the loss is the element substitution at Fe sites.9–12 It has been reported that the magnetic transition temperature and dielectric constants a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.446 922
J. Mater. Res., Vol. 27, No. 6, Mar 28, 2012
http://journals.cambridge.org
Downloaded: 23 Dec 2014
are decreased in the order of RFe2O4, RFeCoO4, RFeCuO4, and RGaCuO4 (R 5 Yb, Lu) samples, which is in connection with the charge transfer between the transition metal 3d orbits.10 In addition, the temperature range of the giant dielectric tunability with electric fields is broadened but the tunable value is decreased through Mg doping.11 These resu
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