We report the magnetic, heat-capacity, dielectric and magnetodielectric (MDE) behaviour of a Haldane spin-chain compound containing light rare-earth ion, Nd2BaNiO5, in detail, as a function of temperature (T) and magnetic field (H) down to 2 K. In addition to the well-known long range antiferromagnetic order setting in at (T_N=) 48 K as indicated in dc magnetization (M), we have observed another magnetic transition near 10 K; this transition appears to be of a glassy-type which vanishes with a marginal application of external magnetic field (even H= 100 Oe). There are corresponding anomalies in dielectric constant as well with variation of T. The isothermal M(H) curves at 2 and 5 K reveal the existence of a magnetic-field induced transition around 90 kOe; the isothermal H-dependent dielectric constant also tracks such a metamagnetic transition. These results illustrate the MDE coupling in this compound. Additionally, we observe a strong frequency dependence of a step in T-dependent dielectric constant with this feature appearing around 25-30 K for the lowest frequency of 1 kHz, far below T_N. This is attributed to interplay between crystal-field effect and exchange interaction between Nd and Ni, which establishes the sensitivity of dielectric measurements to detect such effects. Interestingly enough, the observed dispersions of the T-dependent dielectric constant curves is essentially H-independent in the entire T-range of measurement, despite the existence of MDE coupling, which is in sharp contrast with other heavy rare-earth members in this series.
利用热力学、磁学和介电测量研究了四元尖晶石Mn $_3$ O $_4$中与自旋有序转变相关的介电异常。我们发现，Mn $_3$ O $_4$中的三个磁有序转变中的两个导致了零外加磁场下随温度变化的介电常数的降低.施加磁场的多晶样品离开这两个介电异常几乎不变，但导致介电常数的增加，在中间自旋有序过渡。我们讨论了这种磁介电行为的自旋-声子耦合的可能起源。能带结构的计算表明，在其亚铁磁态，Mn $_3$ O $_4$对应于一个半导体没有轨道简并由于强Jahn-Teller失真。
Dielectric and multiferroic behavior in a Haldane spin-chain compound Sm2BaNiO5 due to an interplay between crystal-field effect and exchange interaction
Field-tunable partial antiferromagnetism, glassy spin dynamics, and magnetodielectric coupling in the quasi-one-dimensional spin-chain compound Ca3CoIrO6
Origin of Large Dielectric Constant with Large Remnant Polarization and Evidence of Magnetoelectric Coupling in Multiferroic La modified BiFeO3-PbTiO3 Solid Solution
