Observation of room temperature magnetodielectric effect in Mn-doped lanthanum gallate and study of its magnetic properties
Observation of room temperature magnetodielectric effect in Mn-doped lanthanum gallate and study of its magnetic properties
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DOI：
10.1039/c6tc03641d
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发表时间：
2016-11
影响因子：
6.4
通讯作者：
H. Rai;S. Saxena;V. Mishra;A. Sagdeo;P. Rajput;R. Kumar;P. Sagdeo
中科院分区：
文献类型：
--
作者：
H. Rai;S. Saxena;V. Mishra;A. Sagdeo;P. Rajput;R. Kumar;P. Sagdeo
采用固相反应法制备了掺锰LaGa1−xMnxO3(LGMO)0≤x≤0.2多晶样品。在印度河2号同步辐射光源的BL-12光束线上进行的粉末X射线衍射实验证实了所有样品的结构相纯度。室温(RT)介电测量是在没有和存在磁场的情况下进行的。在x=0.2(LG8M2O)的LGMO样品中观察到明显的磁介电(MD)效应，即由于施加低磁场而引起介电常数的变化。为了分离在观察到的RT-MD效应中存在的本征贡献和电阻贡献，在RT下进行了磁阻抗阻抗谱(MRIS)测试。目前的磁共振成像分析表明，在与颗粒贡献相对应的频率处(本样品的≥为105赫兹)，观察到的MD现象似乎是目前研究的样品的固有特性，而在较低的探测频率(<；105赫兹)，观察到的变化似乎是由MR(考虑与频率相关的电阻)主导的，这可能是由于Mn3+和Mn4+的共存。XANES(MnK边)谱揭示了Mn3+和Mn4+共存。此外，还进行了RT和低温磁化-磁场(M-H)测量，以及FC和ZFC模式下的M-T测量，以研究磁有序状态。窄的M-H环的出现表明在RT处存在某种磁性有序。此外，在36K附近观察到的铁磁(FM)转变和在5K记录的饱和磁化强度的正常M-H回路证实了低温下的FM有序，而FC-ZFC曲线上的分叉表明低温下FM和反铁磁(AFM)相互作用是竞争的。
Polycrystalline samples of Mn-doped LaGa1−xMnxO3 (LGMO) with 0 ≤ x ≤ 0.2 have been prepared via solid-state reaction method. The structural phase purity of all these samples was confirmed by powder X-ray diffraction experiments carried out at the BL-12 beamline of the Indus-2 synchrotron radiation source. Room-temperature (RT) dielectric measurements were performed in the absence and presence of a magnetic field. A noticeable magnetodielectric (MD) effect, i.e., a change in the value of the dielectric constant owing to the application of a low magnetic field, was observed in the LGMO sample with x = 0.2 (LG8M2O). In order to separate the intrinsic and resistive contributions present in the observed RT MD effect, magnetoresistance impedance spectroscopy (MRIS) was performed at RT. The present MRIS analysis suggests that at frequencies corresponding to the grain contribution (≥105 Hz for the present samples), the observed MD phenomenon appears to be an intrinsic property of the presently studied samples, whereas at lower probing frequencies (<105 Hz) the observed change appears to be dominated by MR (considering frequency-dependent resistance), which was possibly due to the coexistence of Mn3+ and Mn4+. The coexistence of Mn3+ and Mn4+ was revealed by XANES (Mn K-edge) spectroscopy. Moreover, RT and low-temperature magnetization–magnetic field (M–H) measurements, along with M–T measurements in FC and ZFC modes, were performed to investigate the state of magnetic ordering. The appearance of a narrow M–H loop indicates the presence of some magnetic ordering at RT. Furthermore, a ferromagnetic (FM) transition observed around 36 K and a normal M–H loop with saturated magnetization recorded at 5 K confirm FM ordering at low temperatures, whereas a bifurcation in FC-ZFC curves indicates competing FM and antiferromagnetic (AFM) interactions at low temperatures.