The layered perovskites $R$Cr(BO$_3$)$_2$ ($R$ = Y and Ho) with magnetic triangular lattices were studied by performing ac/dc susceptibility, specific heat, elastic and inelastic neutron scattering, and dielectric constant measurements. The results show (i) both samples' Cr$^{3+}$ spins order in a canted antiferromagnetic structure with $T_N$ around 8-9 K, while the Ho$^{3+}$ ions do not order down to $T$ = 1.5 K in HoCr(BO$_3$)$_2$; (ii) when a critical magnetic field H$_{C}$ around 2-3 T is applied below $T_{N}$, the Cr$^{3+}$ spins in the Y-compound and both the Cr$^{3+}$ and Ho$^{3+}$ spins in the Ho-compound order in a ferromagnetic state; (iii) both samples exhibit dielectric constant anomalies around the transition temperature and critical field, but the Ho-compound displays a much stronger magnetodielectric response. We speculate that this is due to the magnetostriction which depends on both of the Cr$^{3+}$ and the Ho$^{3+}$ ions' ordering in the Ho-compound. Moreover, by using linear spin wave theory to simulate the inelastic neutron scattering data, we estimated the Y-compound's intralayer and interlayer exchange strengths as ferromagnetic J$_{1}$ = -0.12 meV and antiferromagnetic J$_{2}$ = 0.014 meV, respectively. The competition between different kinds of superexchange interactions results in the ferromagnetic intralayer interaction.
Magnons and Magnetodielectric Effects in CoCr$_2$O$_4$: Raman Scattering Studies
磁电材料由于其所表现出的丰富的现象而引起了广泛的技术和科学兴趣，包括磁性和铁电性有序的共存，磁介电行为，以及诸如电磁振子的奇异混合激发。多铁性尖晶石材料CoCr $_2$ O $_4$是多铁性材料的一个特别有趣的例子，因为亚铁磁相的磁电行为的证据似乎与传统的非共线自旋驱动机制相冲突。用非弹性光散射方法研究了CoCr $_2$ O $_4$的磁振子和声子谱随温度、压力和磁场的变化.在CoCr $_2$ O $_4$的居里温度（$T_C \sim 94$ K）以下，我们观察到具有T $_{1g}$对称性的$ω\sim 16 \,\text{cm}^{-1}$ $\boldsymbol q=0$磁振子，它具有轴向矢量的变换性质。T $_{1g}$对称磁振子的极大拉曼强度是具有大磁光响应的材料的特征，并且可能由强烈调制CoCr $_2$ O $_4$中的介电响应的大的磁波动引起。的T $_{1g}$ -对称磁振子的拉曼磁化率表现出很强的磁场依赖性，这是一致的磁介电响应中观察到的CoCr $_2$ O $_4$，这表明磁介电行为在CoCr $_2$ O $_4$主要是从磁场依赖性抑制的磁波动，强烈耦合到长波长的声子。随着所施加的压力增加CoCr $_2$ O $_4$中的磁各向异性降低了CoCr $_2$ O $_4$中T $_{1g}$对称性磁振子拉曼磁化率的磁场依赖性，表明应变可用于控制…
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。
In this paper the structural, magnetic, and dielectric properties of langasite compound Pb$_3$TeMn$_3$P$_2$O$_{14}$ have been investigated as a candidate of short-range magnetic correlations driven development of dielectric anomaly above N$\acute{e}$el temperature of ($T_N$=) 7 K. Presence of dielectric anomaly, structural phase transition and a short range magnetic correlation at the same temperature (at around 100 K) as well as magnetic field dependent capacitance clearly indicate that this compound shows magnetodielectric coupling at around 100 K. In addition, unusual behaviour is observed …
Magnetodielectric effect of Bi6Fe2Ti3O18 film under an ultra-low magnetic field
采用金属有机物分解（MOD）法成功制备了具有单相层状钙钛矿结构的Bi 6 Fe 2 Ti 3 O 18磁性铁电薄膜。低温磁电容测量结果表明，在零场冷却条件下，10 Oe的超低磁场可以产生非平凡的磁介电（MD）响应，并且介电常数在磁场中的相对变化为正值，即，当T<55 K时，MD=0.05，而当55 K <T<190 K时，MD为负值，最大值为-0.14。磁介电效应在55 K出现一个符号变化，这是由反铁磁向弱铁磁转变引起的，而在190 K附近磁介电效应突然消失，这可能与钙钛矿结构B位铁离子的有序-无序转变有关。根据铁电薄膜中局域自旋序的准二维唯一性，讨论了Bi_6Fe_2Ti_3O_（18）薄膜的超低场磁介电行为。我们的研究结果为在55 K-190 K的宽温度范围内低成本应用极弱磁场的探测器和开关提供了希望。
Magnetocapacitance as a sensitive probe of magnetostructural changes in NiCr$_2$O$_4$
尖晶石NiCr $_2$ O $_4$的特征在于使用介电和高磁场测量。磁介电响应的趋势落入三个明确的温度制度对应于已知的磁性和结构转变。在65 ° K以上，观察到介电常数对弱磁场的依赖性，没有滞后。当30\，K\，$\leq\,T\,\leq$\，65\，K时，观察到介电常数对磁场的强烈依赖性，并且滞后发展，导致所谓的蝴蝶环。在30 ℃以下，磁介电滞后增强.磁介电磁滞反映了磁滞，表明自旋-自旋相互作用是NiCr $_2$ O $_4$中磁电效应的机制。然而，在高磁场下，磁化强度继续增加，而介电常数饱和。NiCr $_2$ O $_4$的磁介电测量结果表明，在20 K时存在一个额外的先前未观察到的转变。磁性和结构的细微变化表明，这种20，K异常对应于亚铁磁有序化的完成和自旋驱动的结构畸变。我们证明了磁电容是磁结构畸变的灵敏探针。
Magnetodielectric study in SiO2-coated Fe3O4 nanoparticle compacts
研究了表面包覆SiO_2 $_{2}$的Fe $_{3}$ O $_{4}$磁性纳米粒子的介电性能。在高温下，磁场引起的介电常数和介电损耗的变化具有相反的符号和强烈的频率依赖性，这是由非本征磁介质耦合--Maxwell-Wagner效应和磁阻效应共同作用的结果。界面缺陷的存在导致测量中出现明显的迟滞现象。另一方面，在低温下的介电和磁性的强耦合矛盾的Maxwell-Wagner模型，建议内禀磁介电耦合。我们的观测结果与最近的极化开关测量结果相一致，证实了高损耗Fe $_{3}$ O $_{4}$中存在低温多铁态。这种核壳结构为实现低损耗的实用磁电材料提供了一条新的途径。
Field-tunable partial antiferromagnetism, glassy spin dynamics, and magnetodielectric coupling in the quasi-one-dimensional spin-chain compound Ca3CoIrO6
The 6H-perovskites Ba$_3$RRu$_2$O$_9$ (R = rare earth element) demonstrate the magnetodielectric (MD) coupling as a manifestation of $4d - 4f$ magnetic interactions. Here, we have reported a detailed study of the structural, magnetic, heat capacity, and MD properties of the 6H-perovskite Ba$_3$GdRu$_2$O$_9$. The signature of long-range antiferromagnetic (AFM) ordering $\sim$ 14.8 K ($T_N$) is evident from the magnetization and heat capacity studies. The $T_N$ shifts towards the lower temperature side, apart from splitting in two with the application of the magnetic field. Field-dependent magne…
We have demonstrated magnetodielectric (MD) coupling in an Ising-chain magnet Sr2Ca2CoMn2O9, via detailed investigation of ac susceptibility and dielectric constant as a function of temperature, magnetic field and frequency. Sr2Ca2CoMn2O9 consists of spin-chains, made of the regular stacking of one CoO6 trigonal prism with two MnO6 octahedra. The (Co2+ Mn4+ Mn4+) unit stabilizes a (up-down-up) spin-state along the chains which are distributed on a triangular lattice. This compound undergoes a partially disordered antiferromagnetic transition at TN ~ 28 K. The dielectric constant exhibits a cle…
Evidence for reentrant quantum paraelectric state preceded by a multiglass phase with non-classical exponent and magnetodielectric coupling in SrFe12O19
In the present study, we investigated magnetodielectric, magnetoelectric (ME), and angular-dependent polarization in single-crystal Fe4Nb2O9. The magnetodielectric effects in epsilon(x) (x//[100]), epsilon(y) (y//[120]), and epsilon(z) (z//[001]) are found to be significant only around T-N approximate to 95 K when magnetic fields are applied along three orthogonal x-, y- (y//[120]), and z directions. The finite polarization P-x, P-y, and P-z of 70, 100, and 30 mu C/m(2), respectively, can be induced in the antiferromagnetic phase when a finite magnetic field up to 9 T is applied along the thre…
