Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur-721302, India.
J Phys Condens Matter. 2012 Dec 12;24(49):495901. doi: 10.1088/0953-8984/24/49/495901. Epub 2012 Nov 16.
A La(2)NiMnO(6) polycrystalline sample prepared by the sol-gel method showed monoclinic crystal structure with the P2(1)/n space group and a saturation magnetization of 4.63 μ(B)/f.u. at 5 K. Impedance spectroscopy results in the temperature range of 10 K < T < 300 K have revealed a distinct conduction process at grains and grain boundaries, where the grains followed the variable range hopping mechanism and the grain boundaries obeyed Arrhenius thermal activation. A negative magnetoresistance of 2.5% was observed at the paramagnetic to ferromagnetic transition, and this became temperature independent below the magnetic ordering. A marginal positive magnetodielectric (MD) effect that followed the dielectric relaxation was observed and its magnitude was found to decrease with increase of the frequency. A systematic study on the magnetic field induced dielectric properties, dc transport and dc bias effect on the dielectric permittivity has revealed the extrinsic origin of the MD effect in the bulk sample of La(2)NiMnO(6).
采用溶胶-凝胶法制备的 La(2)NiMnO(6)多晶样品具有单斜晶体结构，空间群为 P2(1)/n，在 5 K 时饱和磁化强度为 4.63 μ(B)/f.u.。在 10 K < T < 300 K 的温度范围内进行的阻抗谱研究表明，在晶粒和晶界处存在明显的导电机理，其中晶粒遵循变程跳跃机制，晶界遵循 Arrhenius 热激活。在顺磁到铁磁转变时观察到负磁电阻为 2.5%，在磁性有序以下，该磁电阻变得与温度无关。观察到与介电弛豫相关的微小正磁电（MD）效应，并且发现其幅度随着频率的增加而减小。对磁场诱导介电性能、直流输运和直流偏压对介电常数的影响进行了系统研究，揭示了 La(2)NiMnO(6)体样品中 MD 效应的外在起源。
